2014 European thyroid association guidelines for the management of subclinical hypothyroidism in pregnancy and in children

The application of new concepts of the assessment of the thyroid state to pregnant women

Recently proposed concepts regarding the nature and assessment of the thyroid state have provided a model more consistent with empiric evidence. It now appears likely that there are no such entities as thyroid set points and individual euthyroidism. Rather than there being discrete thyroid states, peripheral organ parameters are associated with thyroid function in a continuous manner. Thyroid hormone levels and, in particular, levels of free thyroxine now appear to be superior to thyrotropin levels as indicators of the thyroid state. Complicating the assessment of the correlations of the thyroid state with pregnancy outcomes are the contribution of the placenta to maternal thyroid function, fetal thyroid development, the multiple potential pathways to any particular outcome, the likely presence of small critical periods of time, the differing genetics of fetal and maternal tissues, and the unreliability of thyroid hormone assays. Nevertheless, there is no apparent reason for there to be a change in pregnancy to the basic principles of thyroid hormone action. The relationships between mild abnormalities of the thyroid state and pregnancy outcomes and the value of treating such mild abnormalities remain uncertain and controversial. The evidence suggests that further investigation of these clinical questions might better be based on thyroid hormone, particularly free thyroxine, levels. In the investigation of borderline low thyroid states, the categories of subclinical hypothyroidism and isolated hypothyroxinemia might both be abandoned with attention being directed to low free thyroxine levels regardless of the thyroid-stimulating hormone (TSH) levels. For these changes to occur, there would ideally be improvements in the assays for free thyroxine in pregnancy. The evidence suggests that, just as in the non-pregnant situation, pregnancy guidelines based on thyrotropin levels may need revision.

Leptin Does Not Influence TSH Levels in Obese Short Children

INTRODUCTION

Growth hormone (GH) and thyroid hormones are important for children growing. In some obese children a slightly elevated TSH concentration is observed. This may be an adaptive mechanism: stimulation of pro-TRH biosynthesis in the hypothalamus in response to elevated leptin. The increased TSH may also reflect the necessity of maintaining the resting energy expenditure or may be a result of inappropriate, low FT4 concentration. Thus, we evaluated serum TSH and FT4 concentrations in idiopathic short stature (ISS) children (non GH-deficient) and examined the effect of children's nutritional status and levels of selected adipocytokines on thyroid function, searching for the presence of various forms of subclinical hypothyroidism, which may be the cause of the slow growth rate.

METHODS

The study group included 115 children (50 girls and 65 boys) with ISS, aged (mean ± SD) 10.4 ± 3.34 years. In each child, lipids, TSH, FT4, IGF-1, maxGH during the stimulation tests, leptin, adiponectin and resistin concentrations were determined. Based on BMI SDS, 3 subgroups: slim (n=26), obese (n=21) and normal weight (n=68) were distinguished.

RESULTS

There was no correlation between leptin level and TSH, FT4 levels. The levels of leptin, total cholesterol and LDL-cholesterol in obese short children were significantly higher than in children from other subgroups. In turn, the levels of adiponectin, resistin, TSH and FT4 did not differ between subgroups. In 7% of children, an elevated TSH level was found (but less than 10 mIU/L), with a similar frequency across subgroups. The higher the leptin, the lower maxGH in clonidine stimulation test was recorded.

CONCLUSIONS

It seems that in obese children with idiopathic short stature leptin does not increase TSH secretion. This may be related to a disruption of the effect of leptin on TSH production and could indicate wide ranging disturbances of hypothalamic signals, and consequently be the cause of inappropriate GH secretion.

Association of maternal triglyceride responses to thyroid function in early pregnancy with gestational diabetes mellitus

INTRODUCTION

The prevalence of Gestational Diabetes Mellitus (GDM) is increasing globally, and high levels of triglyceride (TG) and low levels of free thyroxine (FT4) in early pregnancy are associated with an increased risk of GDM; however, the interaction and mediation effects remain unknown. The aim of the present study is to examine the impact of FT4 and TG combined effects on the prevalence of GDM and the corresponding casual paths among women in early pregnancy.

MATERIALS AND METHODS

This study comprised 40,156 pregnant women for whom early pregnancy thyroid hormones, fasting blood glucose as well as triglyceride were available. GDM was diagnosed using a 2-hour 75-g oral glucose tolerance test (OGTT) according to the American Diabetes Association guidelines, and the pregnant women were grouped and compared according to the results.

RESULTS

An L-shaped association between FT4 and GDM was observed. The prevalence of GDM increased with increasing TG levels. After accounting for multiple covariables, the highest risk for GDM was found among pregnant women of lower FT4 with the highest TG concentrations (odds ratio, 2.44, 95% CI, 2.14 to 2.80; P<0.001) compared with mothers of higher FT4 with the TG levels in the lowest quartile (Q1). There was a significant interaction effect of maternal FT4 and TG levels on the risk for GDM (P for interaction = 0.036). The estimated proportion of the mediating effect of maternal TG levels was 21.3% (95% CI, 15.6% to 36.0%; P < 0.001). In the sensitivity analysis, the mediating effect of TG levels was stable across subgroups.

CONCLUSION

This study demonstrated an L-shaped association between maternal FT4 levels and GDM and the benefit of low TG levels, in which maternal TG levels act as an important mediator in this association. Our findings suggested that pregnant women who treat hypothyroidism should also reduce triglycerides levels in early pregnancy to prevent GDM development.

Does foetal gender influence maternal thyroid parameters in pregnancy?

Objective

It is unknown if foetal gender influences maternal thyroid function during pregnancy. We therefore investigated the prevalence of thyroid disorders and determined first-trimester TSH reference ranges according to gender.

Methods

A cross-sectional study involving 1663 women with an ongoing pregnancy was conducted. Twin and assisted pregnancies and l-thyroxine or antithyroid treatment before pregnancy were exclusion criteria. Serum TSH, free T4 (FT4) and thyroid peroxidase antibodies (TPOAb) were measured at median (interquartile range; IQR) 13 (11-17) weeks of gestation. Subclinical hypothyroidism (SCH) was present when serum TSH levels were >3.74 mIU/L with normal FT4 levels (10.29-18.02 pmol/L), and thyroid autoimmunity (TAI) was present when TPOAb were ≥60 kIU/L.

Results

Eight hundred and forty-seven women were pregnant with a female foetus (FF) and 816 with a male foetus (MF). In women without TAI and during the gestational age period between 9 and 13 weeks (with presumed high-serum hCG levels), median (IQR range) serum TSH in the FF group was lower than that in the MF group: 1.13 (0.72-1.74) vs 1.24 (0.71-1.98) mIU/L; P = 0.021. First-trimester gender-specific TSH reference range was 0.03-3.53 mIU/L in the FF group and 0.03-3.89 mIU/L in the MF group. The prevalence of SCH and TAI was comparable between the FF and MF group: 4.4% vs 5.4%; P = 0.345 and 4.9% vs 7.5%; P = 0.079, respectively.

Conclusions

Women pregnant with an MF have slightly but significantly higher TSH levels and a higher upper limit of the first-trimester TSH reference range, compared with pregnancies with a FF. We hypothesise that this difference may be related to higher hCG levels in women pregnant with a FF, although we were unable to measure hCG in this study. Further studies are required to investigate if this difference has any clinical relevance.

Association of Maternal Mild Hypothyroidism With Offspring Neurodevelopment in TPOAb-Negative Women: A Prospective Cohort Study

OBJECTIVES

Adequate maternal thyroid hormone availability is crucial for fetal neurodevelopment, but the role of maternal mild hypothyroidism is not clear. We aim to investigate the association of maternal mild hypothyroidism with neurodevelopment in infants at 1 year of age among TPOAb-negative women.

METHODS

The present study was conducted within the Jiangsu Birth Cohort. A total of 793 mother-infant pairs were eligible for the present study. Maternal thyroid function was assessed by measuring serum thyroid-stimulating hormone, free thyroxine, and thyroid peroxidase antibodies. Neurodevelopment of infants was assessed by using the Bayley Scales of Infant and Toddler Development third edition screening test (Bayley-III screening test).

RESULTS

In the multivariate adjusted linear regression analyses, infants of women with subclinical hypothyroidism and isolated hypothyroxinemia were associated with decreased receptive communication scores (β = -0.68, p = 0.034) and decreased gross motor scores (β = -0.83, p = 0.008), respectively. Moreover, infants of women with high-normal TSH concentrations (3.0-4.0 mIU/L) and low FT4 concentrations were significantly associated with lower gross motor scores (β = -1.19, p = 0.032), while no differences were observed in infants when the mothers had a high-normal TSH concentration and normal FT4 levels.

CONCLUSIONS

Maternal subclinical hypothyroidism is associated with decreased receptive communication scores in infants at 1 year of age. In addition, maternal TSH concentration greater than 4.0 mIU/L and maternal isolated hypothyroxinemia are associated with impaired gross motor ability of infants, especially in infants of women with high-normal TSH concentrations (3.0-4.0 mIU/L).

Nutrition and Brain Development

All nutrients are essential for brain development, but pre-clinical and clinical studies have revealed sensitive periods of brain development during which key nutrients are critical. An understanding of these nutrient-specific sensitive periods and the accompanying brain regions or processes that are developing can guide effective nutrition interventions as well as the choice of meaningful circuit-specific neurobehavioral tests to best determine outcome. For several nutrients including protein, iron, iodine, and choline, pre-clinical and clinical studies align to identify the same sensitive periods, while for other nutrients, such as long-chain polyunsaturated fatty acids, zinc, and vitamin D, pre-clinical models demonstrate benefit which is not consistently shown in clinical studies. This discordance of pre-clinical and clinical results is potentially due to key differences in the timing, dose, and/or duration of the nutritional intervention as well as the pre-existing nutritional status of the target population. In general, however, the optimal window of success for nutritional intervention to best support brain development is in late fetal and early postnatal life. Lack of essential nutrients during these times can lead to long-lasting dysfunction and significant loss of developmental potential.

Role of pharmacists in management of patients with thyroid disorders

Thyroid dysfunction is one of the most prevalent endocrine disorders, especially common in female patients. If patients are not diagnosed in time or adequately treated, the patients' quality of life can be significantly impaired and additional health problems may occur, considering the key roles of thyroid hormones in the body. Therefore, it is necessary to raise awareness about the importance of recognition of symptoms that may indicate a potential problem with the thyroid gland and help to identify possible causes. For patients who are already being treated with levothyroxine (hypothyroidism), or thiamazole, carbimazole or propylthiouracil (hyperthyroidism), it is necessary to point out the necessity of proper, regular use of the drugs and implementation of accompanying nonpharmacological measures, as well as the potential for the occurrence of adverse reactions and interactions with other drugs or food. A significant role in the mentioned activities should be played by the pharmacist, as the most accessible member of the health team, who can, if necessary, refer the patient to a doctor for diagnosis, monitor the effectiveness and safety of the therapy, and provide appropriate patient counseling.

Establishment of trimester-specific reference intervals for thyroid stimulating hormone and free thyroxine during pregnancy in southwest China by indirect method

OBJECTIVE

A series of physiological changes in thyroid function occur during pregnancy and differ from those non-pregnant women. This study aimed to establish the pregnancy-specific reference intervals of TSH and FT4 using an indirect method based on the healthy pregnant women from southwest China population.

METHODS

Thyroid function test results which available on the Laboratory Information System (LIS) were collected from the pregnancies who visited the Obstetric Clinic or the Department of Gynecology between 1 January 2015, and 30 December 2020. We grouped the data by trimesters to establish the reference intervals (RIs) based on the clinical consensus of different levels of TSH and FT4 at different weeks of gestation. All arrangements were referenced to the document CLSI EP28-A3C.

RESULTS

A total of 33,040 thyroid function test results of pregnant women, aged 31 (28,33) years were statistical analyzed. Estimated RIs for TSH and FT4 in the first, second and third trimesters corresponding to the 2.5^th and 97.5^th percentiles in TPOAb negative were 0.02-5.23, 0.03-5.24, 0.37-5.68 mIU/L, 11.66-20.69, 10.1-18.59, 9.85-16.86pmol/L, respectively.

CONCLUSION

This study provides trimester-specific RIs for TSH and FT4 among healthy pregnant women in southwest China which guides clinicians to diagnosis and screen for thyroid disorders in this region.

Associations of exposure to cadmium, antimony, lead and their mixture with gestational thyroid homeostasis

Maintaining thyroid homeostasis during pregnancy is vital for fetal development. The few studies that have investigated associations between metal exposure and gestational thyroid function have yielded mixed findings. To evaluate the association of exposure to a mixture of toxic metals with thyroid parameters in 824 pregnant women from the Rhea birth cohort in Crete, Greece. Concentrations of three toxic metals [cadmium (Cd), antimony (Sb), lead (Pb)] and iodine were measured in urine using inductively coupled plasma mass spectrometry and thyroid hormones [Thyroid Stimulating Hormone (TSH), free thyroxine (fT4), and free triiodothyronine (fT3)] were measured in serum in early pregnancy. Associations of individual metals with thyroid parameters were assessed using adjusted regression models, while associations of the metal mixture with thyroid parameters were assessed using Bayesian Kernel Machine Regression (BKMR).Women with high (3rd tertile) concentrations of urinary Cd, Sb and Pb, respectively, had 13.3 % (95%CI: 2.0 %, 23.2 %), 12.5 % (95%CI: 1.8 %, 22.0 %) and 16.0 % (95%CI: 5.7 %, 25.2 %) lower TSH compared to women with low concentrations (2nd and 1st tertile). In addition, women with high urinary Cd had 2.2 % (95%CI: 0.0 %, 4.4 %) higher fT4 and 4.0 % (95%CI: -0.1 %, 8.1 %) higher fT3 levels, and women with high urinary Pb had 4 % (95%CI: 0.2 %, 8.0 %) higher fT3 levels compared to women with low exposure. The negative association of Cd with TSH persisted only when iodine sufficiency was unfavorable. BKMR attested that simultaneous exposure to toxic metals was associated with decreased TSH and increased fT3 and revealed a potential synergistic interaction of Cd and Pb in association with TSH. The present results suggest that exposure to toxic metals even at low levels can alter gestational thyroid homeostasis.

First-Trimester Reference Intervals for Thyroid Function Testing among Women Screened at a Tertiary Care Hospital in India

Objectives  Due to differences in the method of assay and population-specific factors, each laboratory needs to establish its own gestation-specific reference intervals (GRIs) for thyroid hormones.

Materials and Methods  Three-hundred forty-one women with less than 14 weeks gestation were screened at a tertiary care hospital in Chhattisgarh, India. Serum levels of thyroid-stimulating hormone (TSH), free thyroxine (fT4), and thyroid peroxidase antibody (anti-TPO) were measured using an ADVIA Centaur XP immunoassay.

GRIs (2.5th and 97.5th percentiles) were determined for TSH and fT4. TSH and fT4 concentrations were converted to multiples of the median (MoM) values. Effect of maternal age, gestational age, and maternal weight was analyzed.

Statistical Analysis  Quantitative variables were expressed as means and standard deviations (SD), and qualitative variables were expressed as frequencies and percentages. Normality of the data was checked using the Kolmogorov–Smirnov test. Values that were normally distributed were expressed only as means and SD. Those that were not normally distributed were expressed as medians and interquartile range. For all statistical analysis, p  < 0.05 was considered as statistically significant.

Results  First-trimester GRI was 0.245 to 4.971 mIU/L for TSH, 10.2 to 18.9 pmol/L for fT4, and 27.0 to 56.89 kIU/L for anti-TPO. There was no significant difference in the mean serum TSH ( p  = 0.920), fT4 ( p  = 0.714), or anti-TPO ( p  = 0.754) values among women in 4 to 7th week and 7 to 14th week of gestation. The 1st and 99th centile MoMs were 0.03 and 4.09 for TSH and 0.66 and 1.39 for fT4. There was a significant positive correlation between the maternal weight and TSH MoM values ( p  = 0.027, r  = 0.120).

Conclusion  These laboratory- and first-trimester-specific GRI for TSH and fT4 shall help in proper diagnosis and treatment of subclinical thyroid dysfunctions. TSH and fT4 MoM values can be used to indicate high or low values in a quantitative manner independent of the reference ranges and may be used by other laboratories.

Age- and sex-specific reference intervals for thyroid hormones in a Chinese pediatrics: a prospective observational study of 1,279 healthy children

BACKGROUND

Thyroid hormones are essential for early neurocognitive development and growth and development in childhood and adolescence. However, the reference intervals (RIs) for thyroid hormones in Chinese pediatric individuals remain unclear. This study aimed to establish thyroid hormone RIs for a Chinese pediatric population according to appropriate age- and sex-specific partitioning.

METHODS

In this prospective observational study, a total of 1,279 healthy children (singletons, aged from 1 day to 12 years) were recruited, and serum samples were analyzed on a Mindray automated chemiluminescence immunoassay analyzer CL-6000i for thyroid hormone detection, including thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), free thyroxine (FT4), total triiodothyronine (T3), and total thyroxine (T4). Age and sex-specific RIs were established, and the corresponding 95% confidence intervals (CIs) were calculated in accordance with the Clinical Laboratory Standards Institute (CLSI) document C28-A3 guidelines.

RESULTS

Quantile testing revealed that the median (P50) and RIs [2.5^th percentile (P2.5)-97.5^th percentile (P97.5)] for TSH, FT3, T3, and T4 of males differed significantly from those of females (P<0.05), except for FT4 (P=0.483). For FT3 and T3, the RIs of males were higher than that of females, and the RI of T4 for males was narrower and higher than that of females [P2.5-P97.5: 72.33-171.60 vs. 72.31-176.27 nmol/L; P50: 116.75 vs. 113.47 nmol/L, P=0.011]. RIs for TSH, FT3, FT4, T3, and T4 showed sex- and age-specific properties and displayed a wide variation during the first month of life but gradually narrowed and concentrated with increasing age. In addition, RIs of TSH, FT3, FT4, and T3 in males differed significantly from females in the first month of life (TSH: 1.46-10.87 vs. 1.08-11.35 mIU/L; FT3: 2.96-7.08 vs. 2.35-7.27 pmol/L, FT4: 13.34-28.65 vs. 13.82-31.83 pmol/L; T3: 0.83-2.33 vs. 0.72-2.46 nmol/L). The RI of T4 also exhibited a difference between males and females in the 9- to 12-year age group (59.31-150.72 vs. 63.29-146.94 pmol/L for males and females, respectively).

CONCLUSIONS

Pediatric RIs of thyroid hormones display age- and sex-specific trends. The RIs established in this study will improve the accuracy of TSH assay result interpretations and clinical decision-making in clinical laboratories that utilize the Mindray analytical platform.

Low-dose short synacthen test with salivary cortisol in patients with suspected central adrenal insufficiency

CONTEXT

The low-dose short synacthen test (LDSST) is recommended for patients with suspected central adrenal insufficiency (AI) if their basal serum cortisol (F) levels are not indicative of an intact hypothalamic-pituitary-adrenal (HPA) axis.

OBJECTIVE

To evaluate diagnostic threshold for salivary F before and 30 min after administering 1 μg of synacthen, performed before 09:30 h.

DESIGN

A cross-sectional study from 2014 to 2020.

SETTING

A tertiary referral university hospital.

PATIENTS

In this study, 174 patients with suspected AI, 37 with central AI and 137 adrenal sufficient (AS), were included.

MAIN OUTCOME MEASURE

The diagnostic accuracy (sensitivity (SE), specificity (SP)) of serum and salivary F levels measured, respectively, by chemiluminescence immunoassay and liquid chromatography-tandem mass spectrometry.

RESULTS

Low basal serum or salivary F levels could predict AI. For the LDSST, the best ROC-calculated threshold for serum F to differentiate AI from AS was 427 nmol/L (SE 79%, SP 89%), serum F > 500 nmol/L reached SP 100%. A salivary F peak > 12.1 nmol/L after administering synacthen reached SE 95% and SP 84% for diagnosing central AI, indicating a conclusive reduction in the likelihood of AI. This ROC-calculated threshold for salivary F was similar to the 2.5th percentile of patients with a normal HPA axis, so it was considered sufficient to exclude AI. Considering AS those patients with salivary F > 12.1 nmol/L after LDSST, we could avoid unnecessary glucocorticoid treatment: 99/150 subjects (66%) had an inadequate serum F peak after synacthen, but salivary F was >12.1 nmol/L in 79 cases, who could, therefore, be considered AS.

CONCLUSIONS

Salivary F levels > 12.1 nmol/L after synacthen administration can indicate an intact HPA axis in patients with an incomplete serum F response, avoiding the need to start glucocorticoid replacement treatment.

Assessment of thyroid function in the preterm and/or very low birth weight newborn

The screening program or early detection of congenital hypothyroidism is one of the greatest advances achieved in Pediatrics. Thyroid hormones are essential for brain development and maturation, which continue into the neonatal stage. Alterations in thyroid function in premature and underweight children in the first months of life causes irreversible damage to the central nervous system and is one of the most frequent and avoidable causes of mental retardation. Diagnosis in the neonatal period is difficult, so it requires an analytical study to be able to carry out the appropriate treatment. The relevance of this problem justifies its communication to all areas of pediatrics. The main objective is to avoid brain damage in these patients. Other aspects to optimize the adequate development of these children with all the necessary periodic controls and to achieve the inclusion of the diagnosis of thyroid alterations during the stay in neonatal units and in the first months of life, need to implement the resources of the health centers and continue advancing according to current knowledge. In this document, we will focus on the screening of preterm newborns VLBW (<32 weeks of gestation) and/or very low weight for gestational age (1500-1000 g VLBW or <1000 g) and the function evaluation protocol thyroid in premature babies. We update the diagnostic procedures, the essential and complementary tests required, the etiology and the differential diagnoses in this pathology.

Maternal adiposity, smoking, and thyroid function in early pregnancy

OBJECTIVE

A high activity of the deiodinase type 2 has been proposed in overweight, obese, and smoking pregnant women as reflected by a high triiodothyronine (T3)/thyroxine (T4) ratio. We speculated how maternal adiposity and smoking would associate with different thyroid function tests in the early pregnancy.

DESIGN

Cross-sectional study within the North Denmark Region Pregnancy Cohort.

METHODS

Maternal thyroid-stimulating hormone (TSH), total T4 (TT4), total T3 (TT3), free T4 (fT4), and free T3 (fT3) were measured in stored blood samples (median gestational week 10) by an automatic immunoassay. Results were linked to nationwide registers, and live-birth pregnancies were included. The associations between maternal adiposity (overweight or obese), smoking, and log-transformed TSH, fT3/fT4 ratio, and TT3/TT4 ratio were assessed using multivariate linear regression and reported as adjusted exponentiated β coefficient (aβ) with 95% CI. The adjusted model included maternal age, parity, origin, week of blood sampling, and diabetes.

RESULTS

Altogether 5529 pregnant women were included, and 40% were classified with adiposity, whereas 10% were smoking. Maternal adiposity was associated with higher TSH (aβ 1.13 (95% CI 1.08-1.20)), whereas maternal smoking was associated with lower TSH in the early pregnancy (0.875 (0.806-0.950)). Considering the T3/T4 ratio, both maternal adiposity (fT3/fT4 ratio: 1.06 (1.05-1.07); TT3/TT4 ratio: 1.07 (1.06-1.08)) and smoking (fT3/fT4 ratio: 1.07 (1.06-1.09); TT3/TT4 ratio: 1.10 (1.09-1.12)) were associated with a higher ratio.

CONCLUSIONS

In a large cohort of Danish pregnant women, adiposity and smoking showed opposite associations with maternal TSH. On the other hand, both conditions were associated with a higher T3/T4 ratio in early pregnancy, which may reflect altered deiodinase activity.

Use of levothyroxine among pregnant women with subclinical hypothyroidism in the United Kingdom: A population-based assessment

Our study aimed to describe levothyroxine prescription patterns and trends over time among pregnant women with subclinical hypothyroidism (SCH) in the United Kingdom.

We used data from the Clinical Practice Research Datalink linked to its Pregnancy Register and the Hospital Episode Statistics database from 1998 to 2017. The study population included women with a diagnosis of SCH or an abnormal thyroid‐simulated hormone (TSH) level one year prior to or during pregnancy. We compared characteristics between women who received a prescription for levothyroxine during pregnancy and those who did not. We further described the timing, dose, duration, and temporal trends of levothyroxine prescriptions.

Our cohort included 6,757 pregnancies from 6,287 women with SCH, of whom 10% received levothyroxine during pregnancy. Among women who received levothyroxine, most received their first prescription during the first trimester (median gestational age: 7 weeks; interquartile range [IQR]: 0, 16) with a median daily dosage of 50 mcg (IQR: 50, 73). Levothyroxine prescription varied over time, decreasing from 23% of pregnant women in 1998 to 7.5% in 2003, remaining stable until 2014, and increasing to 12.5% in 2016. Smoking, diabetes, polycystic ovary syndrome, infertility, timing of SCH diagnosis, age, TSH level at diagnosis, and general practice regions were associated with prescription.

Few women with SCH received levothyroxine during pregnancy, and treatment varied by patient characteristics and geographical regions. These results highlight the need to increase awareness among healthcare providers and will guide future studies that explore barriers to initiating levothyroxine treatment for women with SCH during pregnancy.

Antenatal screening practices in the WHO European Region: a mixed methods study

Background

Literature suggests an increasing trend towards more screening tests, while awareness of potential harms of screenings has been reported to be sub-optimal. This paper aimed to characterize ANC screening practices within the 53 countries of the WHO Europe Region and compare these to evidenced-based recommendations from WHO and from other key reference sources.

Methods

From January 2019 to July 2019 we conducted a survey among key informants (KIs) in the 53 countries of the WHO European Region and a systematic review of literature. KIs were invited to answer an online structured questionnaire, available both in English and Russian. Published and unpublished guidelines, policies or cross-sectional studies on ANC screening practices were searched for in four electronic databases (MEDLINE, Global Health Library, Web of Science, Google) and also sent by KIs. Data obtained from both methods were analysed and triangulated by two independent authors.

Results

Overall 42 countries participated in the survey. Among these, 36 (86%) reported national guidelines on ANC screening, but only 26 (61.9%) reported up-to-date and comprehensive guidelines. All countries reported supplemental use other guidelines, with 19 (45.2%) using more than three. When looking at current evidence-based recommendations, only one (ultrasound before 24 weeks) was reported to be implemented in all countries. Overall, 35 (83.3%) countries reported using at least five not-recommended ANC screening practices, with 21 (50%) implementing ≥10 not-recommended ANC screening practices. The systematic review resulted in 11871 records, with 111 (90 guidelines, 4 policies, 17 cross-sectional studies) matching inclusion criteria. Findings from the systematic review were largely consistent with those of the online survey: among the most comprehensive national guidelines identified, only six (24%) had a concordance ≥75% with the reference recommendations, independently from their publication date, while the few existing cross-sectional studies highlighted large heterogeneity in the implementation of ANC practices among countries.

Conclusions

Guidance on and implementation of evidenced-based recommendations on ANC screening is suboptimal in the WHO European Region. It is necessary to increase the availability of evidence-based high-quality national guidelines and their concrete use in routine practice.

Study on thyroid function test in pregnancy in a tertiary care hospital

Thyroid disorder is a very common endocrine problem encountered by pregnant women. Maternal thyroid dysfunction is associated with adverse outcome both in mother and fetus. The aim of the study: to find out the prevalence of various thyroid disorders in pregnant women attending antenatal clinic. Materials and methods. This prospective cross-sectional study was carried out in the Department of Obstetrics and Gynecology, F.M. Medical College & Hospital, Balasore, Odisha from June 2020 to May 2021. 220 women with uncomplicated singleton pregnancy were included. Serum Thyroid-stimulating hormone (TSH), free T4 (FT4) and free T3 (FT3) were estimated by using electro-chemiluminescence immunoassay technique. Results. Out of 220 pregnant women screened for thyroid dysfunction, 68 were found to have thyroid disorders. 27.3 % of pregnant women had subclinical hypothyroidism, 1.4 % had overt hypothyroidism, 1.8 % had subclinical hyperthyroidism and 0.5 % had overt hyperthyroidism. Prevalence of subclinical hypothyroidism was 6.36 % when the upper reference limit of TSH level taken as 4 mIU/L. Prevalence of thyroid disorder among pregnant women in the age groups 18–25 years, 26–30 years and 31–40 years were 28.9 %, 32.1 % and 38.9 % respectively. There were 35.5 %, 28 % and 26 % pregnant women with thyroid disorders in the first, second and third trimester respectively. Prevalence of both subclinical and overt hypothyroidism were more in multigravida compared to primigravida. Conclusion. Our study revealed high prevalence of thyroid disorders in pregnant women and maternal subclinical hypothyroidism was the most common pattern.

Effect of iodine supplementation in pregnancy on neurocognitive development on offspring in iodine deficiency areas: a systematic review

Objective

To investigate the effect of iodine supplementation during gestation on the neurocognitive development of children in areas where iodine deficiency is common.

Methods

Based on the PRISMA methodology, we conducted the search for articles in the PubMed, LILACS and Scopus databases, between March and April 2020, without limitation of dates. We used descriptors in English, Portuguese, and Spanish, without filters. Four clinical trials and four cohort articles were included in the review.

Results

The maximum supplementation was 300 μg of potassium iodide per day. The Bayley scale and Children's Communication Checklist-Short were used to assess neurodevelopment in children. There was no significant improvement in the children's mental development index and behavioural development index in the supplemented group; however, the psychomotor development index (PDI) showed improvement in the poorer gross motor skills. We found differences in the response time to sound in the supplemented group living in mild deficiency areas.

Conclusion

Daily supplementation with iodine can improve poor psychomotor development of children living in mild to moderate iodine deficiency areas. Thus, it is necessary to perform further studies to assess the effect of supplementation on neurodevelopment before, during and after gestation in mild to moderate iodine deficiency areas.

[Thyroid function of first-trimester twin pregnant women and its association with preterm delivery]

OBJECTIVE

To describe the thyroid function abnormality of first-trimester twin pregnant women according to different references, and to explore its association with preterm delivery.

METHODS

Participants, first-trimester twin pregnant women, were recruited at Peking University Third Hospital from March 2017 to February 2020. The thyroid hormone reference for ordinary adults identified on the assay kits by Siemens incorporation, thyroid hormone reference specifically for singleton pregnancy established previously, and thyroid hormone reference specifically for twin pregnancy established previously were used in the description of hypothyroidism and hyperthyroidism for first-trimester twin pregnant women. Thyroid autoantibody reference identified on the assay kits by Siemens incorporation was used in the description of positive thyroid autoantibody. Multivariable log-binomial regression was conducted to examine the association between thyroid function and preterm delivery, in which normal pregnant women according to the three references and normal pregnant women according to twin pregnancy reference accompanied with negative thyroid autoantibody were taken as control respectively.

RESULTS

A total of 570 twin pregnant women were finally included. Rates of hypothyroidism according to the three references were 1.2%, 1.6% and 3.5%, respectively. Rates of hyperthyroidism according to the three references were 32.6%, 18.1% and 1.1%, respectively. After adjustment for potential confounding factors, risk of preterm delivery significantly increased in pregnant women with hyperthyroidism according to the twin specific pregnancy reference [adjusted relative risk (ARR)=1.41, 95%CI: 1.14-1.75], while no significant increase was found in those with normal thyroid function according to the twin specific pregnancy reference but hyperthyroidism according to the singleton specific pregnancy reference (ARR=1.00, 95%CI: 0.81-1.25) and in those with hyperthyroidism purely according to the ordinary adult reference (ARR=1.06, 95%CI: 0.85-1.32), compared with those normal according to all the references. Risks of preterm delivery almost significantly or significantly increased in pregnant women with hypothyroidism according to the ordinary adult or singleton specific pregnancy reference (ARR=1.40, 95%CI: 0.88-2.22) and those with hypothyroidism according to the twin specific pregnancy reference (ARR=1.53, 95%CI: 1.03-2.28). Overall analysis of thyroid function according to the twin specific pregnancy reference and thyroid autoantibody showed that risks of preterm delivery almost significantly or significantly increased in pregnant women with simple hypothyroidism (ARR=1.46, 95%CI: 0.93-2.27), simple positive thyroid autoantibody (ARR=1.32, 95%CI: 1.15-1.52), and hypothyroidism accompanied with positive thyroid autoantibody (ARR=1.78, 95%CI: 1.30-2.44), compared with those normal according to the twin specific pregnancy reference with negative thyroid autoantibody.

CONCLUSION

The ordinary adult reference and that of singleton pregnancy may lead to under-diagnosis of hypothyroidism and over-diagnosis of hyperthyroidism in first-trimester twin pregnant women. Compared with pregnant women with normal thyroid function, those missed in the diagnosis of hypothyroidism were at a higher risk of preterm delivery, while those over-diagnosed as hyperthyroidism had a similar risk of preterm delivery, indicating a need to develop and generalize twin-pregnancy-specific reference on common indicators of thyroid function. Moreover, the thyroid autoantibody should be taken into consideration in the prenatal diagnosis and treatment to twin pregnant women with hypothyroidism.

Subclinical Hypothyroidism: Prevalence, Health Impact, and Treatment Landscape

Subclinical hypothyroidism (sHypo) is defined as normal serum free thyroid hormone levels coexisting with elevated serum thyroid-stimulating hormone (TSH) levels. sHypo is a common condition observed in clinical practice with several unique features. Its diagnosis should be based on an understanding of geographic and demographic differences in biochemical criteria versus a global reference range for TSH that is based on the 95% confidence interval of a healthy population. During the differential diagnosis, it is important to remember that a considerable proportion of sHypo cases are transient and reversible in nature; the focus is better placed on persistent or progressive forms, which mainly result from chronic autoimmune thyroiditis. Despite significant evidence documenting the health impacts of sHypo, the effects of levothyroxine treatment (LT4-Tx) in patients with sHypo remains controversial, especially in patients with grade 1 sHypo and older adults. Existing evidence suggests that it is reasonable to refrain from immediate LT4-Tx in most patients if they are closely monitored, except in women who are pregnant or in progressive cases. Future research is needed to further characterize the risks and benefits of LT4-Tx in different patient cohorts.

The diagnosis and management of subclinical hypothyroidism is assay-dependent- Implications for clinical practice

OBJECTIVE

We assessed the commutativity of Roche and Abbott thyroid assays in the diagnosis and management of subclinical hypothyroidism (SCH). The Roche and Abbott thyroid assays are used by approximately 75% of clinical laboratories in the UK.

METHOD

Consecutive samples received from primary care on patients with SCH who had a raised thyroid-stimulating hormone (TSH) <10 mIU/L and a normal free thyroxine (fT4) from two laboratories using either Roche or Abbott thyroid assays were identified over 10 working days. Following identification, samples were analysed at the other site within 24 hours. Diagnostic and management discordance were studied using the relevant manufacturer-provided reference ranges.

RESULTS

We identified 93 patients with SCH (53 using the Roche assay). Roche TSH and fT4 results were respectively 40% ± 15% and 16% ± 7% higher (P < .001) compared to Abbott results. Of the 93 patients, 41 (44%) were concordant for SCH on both methods. Of the 53 patients with SCH on the Roche assays, 40 (75.5%) had normal thyroid function and 13 (24.5%) had SCH when analysed using the Abbott assays. Of the 40 patients with SCH on the Abbott assays, 28 (70%) had SCH and 12 (30%) had results indicative for levothyroxine replacement when analysed on the Roche assays. Of these 12 patients, four had TSH > 10 mIU/L, five had low fT4 and three had both.

CONCLUSION

The diagnosis and management of SCH is strikingly different when using TSH and fT4 assays provided by Abbott Laboratories and Roche Diagnostics. Clinicians and laboratorians should be aware that between-assay differences and variations in reference ranges will directly impact the diagnosis and management of subclinical hypothyroidism.

ISOLATED MATERNAL HYPOTHYROXINEMIA AND ITS PERINATAL OUTCOME IN NORTH MACEDONIA

Isolated maternal hypothyroxinemia (IMH) is defined as the presence of low maternal total thyroxine (TT4) level in conjunction with normal maternal thyroid-stimulating hormone (TSH) level. The aim was to investigate whether IMH is associated with adverse pregnancy outcome in North Macedonia. Dried blood spot samples were obtained from 359 pregnant women meeting the inclusion criteria and analyzed for TT4 and TSH. Postpartum data were entered from their medical histories. Out of 359 women, 131 (37.42%) belonged to IMH group. There were statistically significant differences in birth weight (p=0.043), intrauterine growth restriction (IUGR) (p=0.028), Apgar score at 1 min <7 (p=0.018) and cesarean section for dystocia/disproportion (p=0.024) between the IMH and normal thyroid function (NTF) groups. In regression analysis, TSH was a significant variable predicting Apgar score (βst=0.05597, p=0.047), body mass index predicting birth weight (βst=0.02338, p=0.045) and TT4 predicting small for gestational age/IUGR (βst=-0.089834, p=0.029) in IMH group. TT4 was a strong predictor of birth weight (βst=-0.004778, p=0.003) and premature delivery (βst=0.028112, p=0.004) in NTF group. The impact of IMH in pregnancy remains controversial. IMH was associated with an increased maternal BMI and higher birth weight of neonates. Overweight could be a potential risk factor for thyroid dysfunction in pregnant women, and specifically IMH. The worst fetal outcome was seen in IMH mothers examined in second trimester. We found TSH, TT4 and BMI to be strong predictors of perinatal outcomes.

[Assessment of thyroid function in the preterm and/or very low birth weight newborn]

The screening program or early detection of congenital hypothyroidism is one of the greatest advances achieved in Pediatrics. Thyroid hormones are essential for brain development and maturation, which continue into the neonatal stage. Alterations in thyroid function in premature and underweight children in the first months of life causes irreversible damage to the central nervous system and is one of the most frequent and avoidable causes of mental retardation. Diagnosis in the neonatal period is difficult, so it requires an analytical study to be able to carry out the appropriate treatment. The relevance of this problem justifies its communication to all areas of pediatrics. The main objective is to avoid brain damage in these patients. Other aspects to optimize the adequate development of these children with all the necessary periodic controls and to achieve the inclusion of the diagnosis of thyroid alterations during the stay in neonatal units and in the first months of life, need to implement the resources of the health centers and continue advancing according to current knowledge. In this document, we will focus on the screening of preterm newborns VLBW (<32 weeks of gestation) and/or very low weight for gestational age (1500-1000g VLBW or <1000g) and the function evaluation protocol thyroid in premature babies. We update the diagnostic procedures, the essential and complementary tests required, the etiology and the differential diagnoses in this pathology.

"Small Thyroid Gland" in Reproductive Women without Autoimmune Thyroid Disease-Ultrasonographic Evaluation as a Useful Screening Tool for Hypothyroidism

Proper thyroid function is important for women of childbearing age, as hypothyroidism affects fertility, pregnancy and offspring. The upper reference limit for thyrotropin (TSH) in pregnancy was defined as <2.5 mU/L in the first trimester. Recommendations include either universal screening of TSH before pregnancy, or identifying individuals at “high risk” for thyroid illness. “Small thyroid gland” not associated with autoimmune thyroid disease (AITD) seems to be a reason for hypothyroidism and probably should be included in target case finding procedure before pregnancy. The purpose of this cross-sectional study was to analyze relationships between the thyroid volume and its function, and to determine the thyroid volume as a predictive factor for TSH levels above 2.5 µIU/mL in reproductive women without AITD. We included 151 women without AITD, and aged 18–40. Blood and urine samples were analyzed for parameters of thyroid function. Ultrasound examination of the thyroid was performed. The thyroid volume was negatively correlated with TSH. Women with a thyroid volume in the 1st quartile for the study population presented higher TSH levels versus women in the 4th quartile (p = 0.0132). A thyroid volume cut-off point of 9 mL was the predictive factor for TSH levels above 2.5 µIU/mL (p = 0.0037).

Transient Hyperthyrotropinemia in Outpatient Children with Acute Infections of the Respiratory System

Background: Diagnostics of thyroid disorders (TD) are frequently based on the measurements of thyroid stimulating hormone (TSH) concentration only. If TSH is outside the reference range, the diagnostic procedure used in patients with TD isintroduced. Observations indicate that in a considerable number of these patients, TD is not confirmed. The aim of the study was to assess the incidence of transient hyperthyrotropinemia in healthy children during acute infections of the respiratory system. Patients and Methods: The study included consecutive children (49 boys and 45 girls), aged 2.2–17.3 years, who visited one General Practitioner (GP) due to respiratory tract infections. The tests: complete blood count (CBC), C-reactive protein (CRP), TSH and FT4 were run on the next day after the visit at the physician’s (initial visit) and ≥2 weeks after recovery. Results: Among these children, elevated TSH values were found in about 10% of patients, and they went back to normal values after recovery. A prospective analysis showed a reduction of TSH values in approx. 65% of all groups and TSH at the follow-up visit was significantly lower. Conclusions: Transient hyperthyrotropinemia was observed in about 10% of children with acute respiratory tract infection. This preliminary finding remains unexplained.

Subclinical thyroid diseases and isolated hypothyroxinemia during pregnancy

Thyroid diseases in pregnancy are common. While data on management of overt diseases are clear, there is no consensus regarding subclinical thyroid disease. Many studies have tried to clarify the impact of subclinical thyroid disease on pregnancy outcomes without reaching universal conclusions. As several studies are present in literature, but no univocal indication is present to manage each condition, the present review tries to summarize the recent indications for such disease. The most updated guidelines are 2017 American thyroid association for thyroid disease during pregnancy, which at present represent the most accurate and reliable guide. Subclinical hyperthyroidism during pregnancy has not been associated with adverse outcomes and only needs follow up. Subclinical hypothyroidism is associated with adverse obstetric and offspring outcomes. At present thyroxine treatment is recommended in selected cases, as beneficial effects are not clear for all these patients. Data regarding the association between isolated hypothyroxinemia and adverse maternofetal outcome are controversial but treatment is not indicated. Autoimmune thyroid disease represents the main thyroid risk factor for adverse pregnancy outcomes. If patients have normal TSH values, treatment is not indicated. A possible thyroxine treatment can be evaluated on a case-by-case basis in euthyroid patients with history of abortion/infertility. In the last years, risks of subclinical thyroid dysfunction on the outcome of gestation and new-born have been scaled back. Further prospective studies are necessary to better understand thyroid dysfunction in pregnancy to perfectly target treatment in appropriate settings.

Congenital Hypothyroidism due to a Low Level of Maternal Thyrotropin Receptor-Blocking Antibodies

INTRODUCTION

Maternal TSH receptor antibodies (TRAbs) can cross the placenta and affect fetal and neonatal thyroid function. Maternal TSH receptor-blocking antibodies (TBAbs) are a rare cause of congenital hypothyroidism.

CASE REPORT

Following the discovery of a highly elevated TSH on her neonatal screening test, a 10-day-old girl with no familial history of thyroid disorder was referred to the pediatric endocrinology unit. Hypothyroidism was confirmed with a highly elevated TSH (817 mIU/L, reference range 0.4-3.1) and very low levels of FT4 (1.8 pmol/L, reference range 12-22). Anti-TPO antibodies were at 81 IU/mL (reference range <34), TRAbs at 1.7 IU/L (reference range <1.75), and thyroglobulin at 9.4 µg/L (reference range 3.5-77). The thyroid appeared normal on ultrasonography, and no radioiodine uptake was seen on the scintigraphy after the perchlorate discharge test. Concomitantly, a severe maternal hypothyroidism was discovered (TSH 224 mIU/L). The maternal ultrasound appeared normal, anti-TPO antibodies were moderately elevated, and TRAbs were at 3.2 IU/L. TBAbs activity was measured in the mother and her daughter, and a very high and similar blocking activity was observed in both patients (TBAbs 89%, reference range <10%). L-thyroxine treatment was introduced in the newborn and was successfully discontinued at 6.5 months of age, as the TBAbs activity decreased.

CONCLUSION

We report herein a case of transient congenital hypothyroidism with a normal neonatal TRAbs level. In case of maternal TBAbs, similar activity of maternal TBAbs must be expected in the neonate, independently of the neonatal level of TRAbs.

Avoidance of iodine deficiency/excess during pregnancy in Hashimoto's thyroiditis

PURPOSE

 Hashimoto's thyroiditis is a common disease that also affects pregnant women. We analyzed to what extent the inflammatory process of Hashimoto's thyroiditis changes with iodine prophylaxis in pregnant women. The target for immunologic activity was levels of thyroid antibodies (TPO).

METHODS

 The data were collected retrospectively from 20 consecutive, pregnant patients who had been diagnosed with Hashimoto's thyroiditis between 01.12.2012 and 01.12.2014 and had received iodine supplementation with 100 µg (n = 1) or 150 µg (n = 19). At least two measurements of TPO antibody levels taken during pregnancy and one after pregnancy were evaluated for each patient in the study group.

RESULTS

 At the end of pregnancy, the average TPO antibody level for the 20 patients studied was 137 IU/ml (+/-214 IU/ml), the lowest being 16 IU/ml and the highest 1000 IU/ml. Despite iodine prophylaxis, levels of TPO antibodies decreased in 18 patients during pregnancy, falling below the reference value of 35 IU/ml in 5 cases. However, in one patient TPO antibodies increased from 60 IU/ml to 237 IU/ml during pregnancy while in another, levels remained constant at 1000 IU/ml.

CONCLUSION

 Iodine prophylaxis in pregnant women, taken at a dose of 100 or 150 μg daily was shown to have no negative systemic effects on Hashimoto's thyroiditis in a group of pregnant women with increased TPO levels, and can therefore be recommended for expectant mothers, including those with this disease.

Relationship between Thyroid Status during the First Trimester of Pregnancy and Neonatal Well-Being

Iodine is an essential micronutrient for the synthesis of thyroid hormones. The proper functioning of the thyroid axis is essential for the normal development of the nervous system, especially in the first trimester of gestation. The aim of the present study was to analyze the perinatal outcomes, anthropometry, and APGAR test scores of newborns and to relate them to maternal thyroid status. A total of 190 newborns participated in the study. No correlation was found between thyroid stimulating hormone (TSH) and maternal ioduria values in the first trimester of gestation with the weight or length of the newborn, or the APGAR score at one minute after birth. However, we found significant differences between the APGAR scores of children whose mothers had an iodine sufficiency level in the first trimester compared to the children of mothers with iodine deficiency. Similarly, the APGAR scores of children whose mothers had a TSH > 4 have significantly better APGAR scores than the children of mothers with a TSH < 4. Likewise, we found significant differences between the measurements of the newborns depending on whether their mothers smoked. The children of mothers who took iodine supplements or iodized salt obtained the highest APGAR score at one and five minutes after birth. It is essential to focus on recommending adequate consumption of iodine supplements and iodized salt prior to gestation and at least during the first trimester to achieve better fetal well-being.

Treatment of subclinical hypothyroidism: assessing when treatment is likely to be beneficial

Introduction: Subclinical hypothyroidism (SCH) is a common condition diagnosed in up to 16% of the population. SCH is diagnosed when serum TSH is high and circulating thyroid hormones are within the reference range. SCH is considered to be a mild form of thyroid failure by some due to the log-linear relationship between TSH and thyroid hormones. Nevertheless, it is unclear whether the treatment of SCH with thyroid hormones is beneficial, and hence, it is not surprising that expert opinions and recommendations from societies differ in their opinions on how best to manage SCH.Areas covered: This article reviews the currently available evidence pertaining to SCH and provides recommendations as to when treatment of SCH should be considered. An electronic search of PubMed from 1970 to 2019 was performed and systematically reviewed studies assessing the effects of treatment in SCH. The main areas that are considered are the effects of treatment on symptoms and quality of life, and important clinical consequences including psychocognitive outcomes and cardiovascular events.Expert opinion: Treatment of SCH with thyroid hormones is debated and the current literature in this area lacks clarity. We provide an evidence-based recommendation for when treatment of SCH with thyroid hormones should be considered.

Effect of thyroxine treatment on pregnancy outcomes in infertile Japanese women with TSH levels between 2.5 μIU/mL and the upper reference limit: a retrospective study

Recent randomized controlled studies have revealed that levothyroxine (LT4) treatment improves pregnancy outcomes only in infertile women with subclinical hypothyroidism who have thyroid autoantibodies (TAs), but not for those with high TSH levels within the normal range who have TAs. Here, we retrospectively investigated pregnancy outcomes in infertile Japanese women with 2.5 μIU/mL ≤ TSH < upper reference limit (URL). Between 2012 and 2018, 286 patients diagnosed with infertility were followed for more than 1 year at our institution. Among them, we included 106 patients with 2.5 μIU/mL ≤ TSH < URL. We divided these patients into four groups based on the combination of TA positivity and LT4 treatment status to assess the effects of LT4 treatment considering TA positivity on the incidence of pregnancy or miscarriage. In this study, we did not find any significant differences in the rates of pregnancy or miscarriage among the four groups (p = 0.81 and 0.52, respectively). In addition, logistic regression analysis showed that age and history of miscarriage were associated with the incidence of pregnancy, but presence of TAs and LT4 treatment status were not and that no variables examined were associated with the incidence of miscarriage. In summary, we were not able to demonstrate the benefit of LT4 treatment for pregnancy outcomes in Japanese euthyroid infertile women with 2.5 μIU/mL ≤ TSH < URL regardless of TA status in this study.

A randomized, double-blind study of iodine supplementation during pregnancy in Sweden: pilot evaluation of maternal iodine status and thyroid function

Purpose

Pregnant women in Sweden are mildly iodine deficient. We investigated the effect of daily iodine supplementation on the iodine and thyroid status of pregnant women.

Methods

In this pilot, randomized, double-blind trial, 200 thyroid-healthy pregnant women were recruited at mean (standard deviation) pregnancy week 8.85 (1.62) and assigned (1:1) to daily intake of a multivitamin tablet with or without 150 μg of iodine. Urine and serum samples were collected at baseline and once during the second and third trimesters. Urinary iodine concentration (UIC), serum thyroglobulin (Tg), thyroid-stimulating hormone (TSH), free thyroxine (FT4), and thyroid peroxidase antibodies (TPOabs) were analyzed. Neonatal TSH data were collected. UIC and Tg were also analyzed in a group of 89 thyroid-healthy non-pregnant women of reproductive age (WRA).

Results

At baseline, the intervention and the control groups had similar median UIC (interquartile range (IQR)): 110 μg/L (74–119) and 111 μg/L (66–168), respectively. The intervention group reached iodine sufficiency with median UIC (IQR) 139 μg/L (89–234) and 136 μg/L (91–211) in the second and third trimester, respectively, without significant difference from the lower limit of the recommended range, i.e. 150–250 μg/L (p = 0.42 and p = 0.87, respectively). The intervention group had higher median UIC and lower median Tg compared to the control group during the second (p < 0.001 and p = 0.019, respectively) and third trimester (p < 0.001 and p = 0.003, respectively), whereas thyroid hormones, serum TPOabs, and neonatal TSH were similar. The WRA group presented median UIC (IQR) 65 μg/L (30–98) and median Tg (IQR) 18 μg/L (13–27).

Conclusion

A daily supplement containing 150 μg of iodine to a group of pregnant women with mild iodine deficiency improved the iodine status from mild ID to iodine sufficiency. This improvement seems to have had a positive impact on maternal thyroglobulin. This study is now under extension to investigate the children’s neuropsychological development.

Trial registration

ClinicalTrials.gov Identifier NCT02378246, May 3, 2015, retrospectively registered.

Prevalence of Hypothyroidism in Pregnant Women in India: A Meta-Analysis of Observational Studies

INTRODUCTION

This meta-analysis was conducted to estimate the prevalence of hypothyroidism among pregnant women in India.

METHODS

We searched PubMed, Web of Science, Scopus, Google Scholar, and Shodhganga (Indian thesis repository) for observational studies, providing prevalence of hypothyroidism among pregnant women in India. Systematic study selection and data extraction procedures were followed. Quality assessment of each study was done using JBI critical appraisal checklist. The random effects model was used for pooling the effect sizes. Publication bias was assessed using the funnel plot and rank correlation test. I 2 statistics was used to measure heterogeneity across the studies. Heterogeneity in the pooled estimates was further explored with subgroup analyses and meta-regression analysis.

RESULTS

Sixty-one studies were found eligible and included in this review. The pooled estimate of the prevalence of hypothyroidism in pregnant women was 11.07% (95% CI: 8.79-13.84, I 2 = 99%). Pooled prevalence estimates of subclinical and overt hypothyroidism are 9.51% (95% CI: 7.48-12.04, I 2 = 98%) and 2.74% (95% CI: 2.08-3.58, I 2 = 94%).

CONCLUSION

We documented 11.07% pooled prevalence of hypothyroidism in pregnant women in India.

European Biological Variation Study (EuBIVAS): within- and between-subject biological variation estimates for serum thyroid biomarkers based on weekly samplings from 91 healthy participants

OBJECTIVES

Thyroid biomarkers are fundamental for the diagnosis of thyroid disorders and for the monitoring and treatment of patients with these diseases. The knowledge of biological variation (BV) is important to define analytical performance specifications (APS) and reference change values (RCV). The aim of this study was to deliver BV estimates for thyroid stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), thyroglobulin (TG), and calcitonin (CT).

METHODS

Analyses were performed on serum samples obtained from the European Biological Variation Study population (91 healthy individuals from six European laboratories; 21-69 years) on the Roche Cobas e801 at the San Raffaele Hospital (Milan, Italy). All samples from each individual were evaluated in duplicate within a single run. The BV estimates with 95% CIs were obtained by CV-ANOVA, after analysis of variance homogeneity and outliers.

RESULTS

The within-subject (CV _I ) BV estimates were for TSH 17.7%, FT3 5.0%, FT4 4.8%, TG 10.3, and CT 13.0%, all significantly lower than those reported in the literature. No significant differences were observed for BV estimates between men and women.

CONCLUSIONS

The availability of updated, in the case of CT not previously published, BV estimates for thyroid markers based on the large scale EuBIVAS study allows for refined APS and associated RCV applicable in the diagnosis and management of thyroid and related diseases.

Pregnancy-related reference intervals for serum thyrotropin based on real-life clinical data

AIM

During pregnancy, thyroid homeostasis is physiologically modified, leading to altered levels of thyrotropin (TSH): hence, the adoption of pregnancy-related, population- and method-specific reference ranges is recommended. This monocentric and retrospective study was conducted to establish local pregnancy-related reference intervals for serum TSH in singleton pregnant women using real-life clinical data.

METHODS

We included women who measured serum TSH during pregnancy at our Laboratory over six years, excluding pregnant women with current or past history of thyroid disease, pituitary or autoimmune diseases, use of medications known to influence thyroid function, multiple and/or pathological pregnancies, BMI >30 Kg/m².

RESULTS

We retrieved a total of 3744 TSH results. Reference limits (90% confidence intervals) for TSH (in mIU/L) are: first trimester 0.09 (0.06-0.12) - 3.16 (3.05-3.29); second trimester 0.25 (0.11-0.30) - 3.55 (3.34-3.73); third trimester 0.42 (0.15-0.48) - 3.93 (3.80-4.08).

CONCLUSION

In conclusion, real-life clinical data could be used to establish or verify local reference intervals for TSH in pregnant women: this may reduce the risk of misclassification of pregnant women undergoing thyroid function testing.

Hyperthyroidism in pregnancy: evidence and hypothesis in fetal programming and development

The management of hyperthyroidism in pregnant patients has been a topic of raised clinical awareness for decades. It is a strong recommendation that overt hyperthyroidism of Graves' disease in pregnant women should be treated to prevent complications. The consequences of hyperthyroidism in pregnancy are less studied than hypothyroidism, and a literature review illustrates that the main burden of evidence to support current clinical guidance emerges from early observations of severe complications in Graves' disease patients suffering from untreated hyperthyroidism in the pregnancy. On the other hand, the more long-term consequences in children born to mothers with hyperthyroidism are less clear. A hypothesis of fetal programming by maternal hyperthyroidism implies that excessive levels of maternal thyroid hormones impair fetal growth and development. Evidence from experimental studies provides clues on such mechanisms and report adverse developmental abnormalities in the fetal brain and other organs. Only few human studies addressed developmental outcomes in children born to mothers with hyperthyroidism and did not consistently support an association. In contrast, large observational human studies performed within the last decade substantiate a risk of teratogenic side effects to the use of antithyroid drugs in early pregnancy. Thus, scientific and clinical practice are challenged by the distinct role of the various exposures associated with Graves' disease including the hyperthyroidism per se, the treatment, and thyroid autoimmunity. More basic and clinical studies are needed to extend knowledge on the effects of each exposure, on the potential interaction between exposures and with other determinants, and on the underlying mechanisms.

Thyroid function testing and management during and after pregnancy among women without thyroid disease before pregnancy

BACKGROUND

Screening in pregnancy for subclinical hypothyroidism, often defined as thyroid-stimulating hormone (TSH) greater than 2.5 mIU/L or greater than 4.0 mIU/L, is controversial. We determined the frequency and distribution of TSH testing by gestational age, as well as TSH values associated with treatment during pregnancy and the frequency of postpartum continuation of thyroid hormone therapy.

METHODS

We performed a retrospective cohort study of pregnancies in Alberta, Canada. We included women without thyroid disease who delivered between October 2014 and September 2017. We used delivery records, physician billings, and pharmacy and laboratory administrative data. Our key outcomes were characteristics of TSH testing and the initiation and continuation of thyroid hormone therapy. We calculated the proportion of pregnancies with thyroid testing and the frequency of each specific thyroid test.

RESULTS

Of the 188 490 pregnancies included, 111 522 (59.2%) had at least 1 TSH measurement. The most common time for testing was at gestational week 5 to 6. Thyroid hormone therapy was initiated at a median gestational age of 7 (interquartile range 5-12) weeks. Among women with first TSH measurements of 4.01 to 9.99 mIU/L who were not immediately treated, the repeat TSH measurement was 4.00 mIU/L or below in 67.9% of pregnancies. Thyroid hormone was continued post partum for 44.6% of the women who started therapy during their pregnancy.

INTERPRETATION

The findings of our study suggest that current practice patterns may contribute to overdiagnosis of hypothyroidism and overtreatment during pregnancy and post partum.

Pregnancy and Neonatal Outcomes With Levothyroxine Treatment in Women With Subclinical Hypothyroidism Based on New Diagnostic Criteria: A Systematic Review and Meta-Analysis

BACKGROUND

Subclinical hypothyroidism (SCH) during pregnancy has been associated with multiple adverse maternal and neonatal outcomes. However, the potential benefits of levothyroxine (LT4) supplementation remain controversial. Variations across studies in diagnostic criteria for SCH may, in part, explain the divergent findings on the subject. This study aimed to assess the effect of LT4 treatment on pregnancy and neonatal outcomes among pregnant women who were diagnosed as SCH based on the most recent diagnostic criteria.

METHODS

We conducted a systematic review and meta-analysis of the literature published from inception to January 2020. The search strategy targeted the studies on pregnancy and neonatal outcomes following LT4 treatment in women with SCH based on 2017 American Thyroid Association diagnostic criteria. Pooled effect sizes were estimated using fixed and random effect models, according to the absence or presence of heterogeneity which was assessed using the I-squared statistic. Sources of heterogeneity and the stability of results were evaluated through sensitivity analysis.

RESULTS

Of the 2781 identified references, 306 full-text articles were screened for eligibility. Finally, 6 studies including a total of 7955 participants were retained for analysis. Summary effect estimates indicated that pregnant women with SCH treated with LT4 had a lower risk of pregnancy loss [odds ratio (OR) = 0.55, 95% confidence interval (CI): 0.43-0.71], preterm birth (OR=0.63, 95% CI: 0.41-0.98) and gestational hypertension (OR = 0.78, 95% CI: 0.63-0.97) than those in control group.

CONCLUSION

LT4 treatment in pregnant women with SCH may reduce the risk of pregnancy loss, preterm delivery and gestational hypertension.

Early Levothyroxine Treatment for Subclinical Hypothyroidism or Hypothyroxinemia in Pregnancy: The St Carlos Gestational and Thyroid Protocol

The optimal maternal levels of thyroid hormones (TH) during the first trimester of gestation have not been established, nor has the ideal moment to initiate levothyroxine treatment (LT) to improve the evolution of gestation and fetal development. Cut-off points for Thyroid-stimulating hormone (TSH) <2.5 µIU/mL and free thyroxine (FT4)>7.5 pg/mL have been recommended. There are no data on whether initiation of LT <9th Gestational Week (GW) can have a favourable impact.

OBJECTIVE

To define the TSH/FT4 percentiles corresponding with 2.5 µIU/mL and 7.5 pg/mL levels, respectively, at GW8 (Study 1), and evaluate the effects of protocol-based LT before GW9 on gestation evolution, in women with TSH ≥2.5 µIU/mL and/or FT4≤ 7.5 pg/mL (study 2).

SUBJECTS

2768 consecutive pregnant women attending the first gestational visit from 2013-2014 and 3026 from 2015-2016 were eligible for Study I and 2 respectively. A final 2043 (study 1) and 2069 (study 2) women were assessed in these studies.

RESULTS

Study 1: The FT4 level of 7.5 pg/mL corresponds with the 17.9th percentile, a TSH level of 2.5 µIU/mL with the 75.8^th. Women with TSH ≥2.5 µIU/mL had a history of fetal losses more frequently than those <2.5 (OR 2.33 (95%CI): 1.58-3.12), as did those with FT4 ≤7.5 pg/ml compared to those >7.5 (OR 4.81; 3.25-8.89). Study 2: A total of 1259 women had optimal TSH/FT4 levels (Group 1), 672 (32.4%, Group 2) had suboptimal TSH or T4l, and 138 (6.7%, Group 3) had suboptimal values of both. 393 (58.5%) in Group 2 and 88 (63.8%) in Group 3 started LT before GW9. Mean (SD) GW24 levels were TSH: 1.96 ± 1.22 µIU/mL and FT4: 7.07 ± 1.25 pg/mL. The highest FT4 value was 12.84 pg/mL. The adjusted risk for an adverse event if LT was started early was 0.71 (0.43-0.91) for Group 2 and 0.80 (0.66-0.94) for Group 3.

CONCLUSIONS

Early LT in women with suboptimum levels of TSH/FT4 (≥2.5µIU/mL/≤7.5 pg/ml) at or before GW9 is safe and improves gestation progression. These data support the recommendation to adopt these cut-off points for LT initiation, which should be started as early as possible.

Inadequate iodine intake in lactating women in Sweden: A pilot 1-year, prospective, observational study

INTRODUCTION

Breastfed infants depend on breast-milk iodine for growth and brain development, as iodine is a trace element important for thyroid hormone production. Iodine need is higher during lactation; hence, mothers and children are at risk of iodine deficiency. We aimed to explore maternal iodine and thyroidal status during lactation.

MATERIAL AND METHODS

Pregnant women were recruited in Gothenburg, southwest Sweden. Maternal urine and serum were collected at pregnancy week 35-37 (n = 84) and 0.5, 4, and 12 months postpartum. Seventy mothers provided breast milk at 0.5 months.

RESULTS

Median (interquartile range) breast-milk iodine concentration was 90 (66-116) μg/L. About 58% had breast-milk iodine concentration <100 μg/L. Iodine supplement users (n = 13) had higher breast-milk iodine concentration than non-users (n = 49) (140 μg/L vs 71 μg/L, P = .001). Exclusively breastfeeding women at 4 months postpartum (n = 57) had lower median urinary iodine concentration (85 μg/L vs 133 μg/L, P = .004) and higher thyroglobulin serum concentration (22.3 μg/L vs 11.8 μg/L, P = .032) than non-exclusively breastfeeding women (n = 25). Concentrations of thyroid hormones were unaffected.

CONCLUSIONS

This pilot study suggests that lactating women in southwest Sweden present mildly inadequate iodine intake, mainly among non-iodine supplement users and exclusively breastfeeding mothers. Studies on the coverage of the iodine fortification program in breastfeeding women are warranted.

Subclinical Hypothyroidism as the Most Common Thyroid Dysfunction Status in Children With Down's Syndrome

INTRODUCTION

Thyroid dysfunctions are one of the most common abnormalities coexisting in children with Down's syndrome (DS) and have been reported in up to 54% of cases.

AIM OF THE STUDY

The purposes of this retrospective study were to investigate the course of subclinical hypothyroidism in children with DS, to evaluate the thyroid function of these subjects in relation to the risk of developing overt thyroid disease and autoimmunity, and to identify clinical and biochemical characteristics of patients prescribed L-T4 therapy in children and adolescents with DS and SH.

MATERIAL AND METHODS

The records of DS patients referred to the Endocrinology Outpatient Clinic between 2010 and 2015 for screening of thyroid function were observed till the end of 2019 June and analyzed retrospectively. The children diagnosed with congenital hypothyroidism, acute lymphoblastic leukemia, and seizures and treated with drugs that may have interfered with thyroid function like lithium, antiepileptic, or iodinated drugs and glucocorticoids were excluded from the study.

RESULTS

The data of 77 DS patients were collected, evaluated, and analyzed. The study group consisted of 73 patients (32 girls and 41 boys with the mean age at baseline of 3.0 ± 4.5 years). A total of 63/73 (87%) children were diagnosed with SH. The 16/63 (25.4%) patients were followed-up without the treatment (group SH-T0), and therapy with levothyroxine (L-T4) was introduced in 47/63 (74.6%) SH children with a mean dosage of 1.8 ± 1.0 μg/kg/day (group SH-T1). Thyroxine supplementation did not improve growth expressed as ΔhSDS (0.1 ± 1.3, ranged -2.1 to 3.8 in SH-T0 vs. 0.0 ± 0.7, ranged -1.7 to 1.4 in SH-T1, p = 0.96) and ΔBMI Z-score (0.3 ± 0.9, ranged -0.9 to 2.6 in SH-T0 vs. 0.3 ± 1.1, ranged -2.1 to 2.9 in SH-T1, p = 0.65). Positive anti-TPO and anti-TG antibodies were detected in 7/63 (11.1%) DS cases.

CONCLUSIONS

SH is the most frequent presentation of thyroid gland dysfunction in DS children. A small percentage of patients develop an overt hypothyroidism, particularly in females with mostly positive titer of antithyroid autoantibodies.

Toward a science-based testing strategy to identify maternal thyroid hormone imbalance and neurodevelopmental effects in the progeny - part I: which parameters from human studies are most relevant for toxicological assessments?

The 2018 European Food Safety Authority/European Chemicals Agency Guidance on the Identification of Endocrine Disruptors lacks clarity on how the presence or absence of substance-induced maternal thyroid hormone imbalance, or the potential for subsequent deleterious consequences in child neurodevelopment, should be established by toxicological assessments. To address these uncertainties, this narrative review evaluates human evidence on how altered maternal thyroid function may be associated with child neurodevelopmental outcomes; and seeks to identify parameters in human studies that appear most relevant for toxicological assessments. Serum levels of free thyroxine (fT4) and thyroid stimulating hormone (TSH) are most frequently measured when assessing thyroid function in pregnant women, whereas a broad spectrum of neurodevelopmental parameters is used to evaluate child neurodevelopment. The human data confirms an association between altered maternal serum fT4 and/or TSH and increased risk for child neurodevelopmental impairment. Quantitative boundaries of effects indicative of increased risks need to be established. Moreover, it is unknown if altered serum levels of total T4, free or total triiodothyronine, or parameters unrelated to serum thyroid hormones might be more relevant indicators of such effects. None of the human studies established a link between substance-mediated liver enzyme induction and increased serum thyroid hormone clearance, let alone further to child neurodevelopmental impairment. This review identifies research needs to contribute to the development of toxicity testing strategies, to reliably predict whether substances have the potential to impair child neurodevelopment via maternal thyroid hormone imbalance.

[Diagnostic and treatment of subclinical hypothyroidism in pregnant and planning pregnancy patients: modern view of the problem]

There is no universal diagnostic and treatment strategy of subclinical hypothyroidism (SHT) in pregnant women and those who are planning pregnancy due to differences in population-specific and trimester-specific thyroid-stimulating hormone (TSH) reference values, influence of thyroid autoimmunity markers on pregnancy outcomes, adherence to fixed universal cutoff concentrations TSH in Russia and multidisciplinary team care with different treatment opinions involving. An absence of universal approach to SHT leads to excess treatment, financial and psychological burden on pregnant women.Up to American Thyroid Association (ATA) Guidelines 2017 and project of Clinical Guidelines of Russian Association of Endocrinologists 2019 a treatment strategy of SHT should be left up to the endocrinologist to choose. In our paper we systematize global scientific and clinical experience of planning and management pregnancies with SHT to help physicians to choose treatment option based on principals of evidence-based medicine.

Consequences of Iodine Deficiency and Excess in Pregnancy and Neonatal Outcomes: A Prospective Cohort Study in Rio de Janeiro, Brazil

Background: Insufficient or excessive iodine intake during gestation may compromise adaptive mechanisms in maternal thyroid function and lead to adverse pregnancy outcomes. In this context, we aimed to study the effects of maternal iodine status in the first and third trimesters of gestation on obstetric and neonatal outcomes in an iodine-sufficient population in Rio de Janeiro, Brazil. Methods: A total of 214 pregnant women in the first trimester of gestation were enrolled and prospectively followed until delivery between 2014 and 2017. All participants were ≥18 and ≤35 years, had a spontaneous single pregnancy, and had no history of thyroid or other chronic diseases, nor were they taking iodine-containing supplements at enrollment. In the first trimester, we obtained clinical information and determined thyroid function and the urinary iodine concentration (UIC) of the participants. Thyroid function and UIC were reassessed in the third trimester. Iodine status was determined by the median of UIC obtained from six urine spot samples by the inductively coupled plasma mass spectrometry method. Pregnancy and neonatal outcomes and delivery information were obtained from medical records. Results: The median UIC in the whole population was 219.7 μg/L. The prevalence of UIC <150 μg/L was 17.2%, and 38.7% had UIC ≥250 μg/L. Gestational diabetes (GDM) was higher in the group with UIC 250-499 μg/L (n = 77) compared with the group with UIC 150-249 μg/L (n = 94) (20.3% vs. 9.7%, p < 0.05). Ultimately, UIC ≥250 μg/L was an independent risk factors for GDM (relative risk [RR] = 2.9 [confidence interval, CI = 1.1-7.46], p = 0.027) and hypertensive disorders of pregnancy (HDP) (RR = 4.6 [CI = 1.1-18.0], p = 0.029). Among 196 live-born newborns, lower birth length was observed in infants whose mothers had UIC <150μg/L (n = 37) in the first trimester compared with those with UIC 150-249 μg/L (n = 86) (median interquartile range: 48.0 [2.2] vs. 49.0 [4.0] cm, p = 0.01). Maternal UIC <150 μg/L was negatively associated with birth length of newborns (Exp (B) = 0.33 [CI = 0.1-0.9], p = 0.03). Conclusions: In a population whose median iodine intake is sufficient, extensive individual variation occurs. Such abnormalities are associated with increased GDM and HDP when UIC is ≥250 μg/L, and lower infant birth length when UIC is <150 μg/L.

The Association Between Isolated Maternal Hypothyroxinemia in Early Pregnancy and Preterm Birth

Background: The association between isolated maternal hypothyroxinemia (IMH) during pregnancy and preterm birth (PTB), especially for subtypes of PTB, is unclear. This study aimed at determining the association between IMH diagnosed in early pregnancy and PTB, with further investigation into various subtypes of PTB. Methods: This study included 41,911 pregnant women (963 with IMH and 40,948 euthyroid women) who underwent first-trimester prenatal screening at the International Peace Maternity and Child Health Hospital (IPMCH) in Shanghai, China between January 2013 and December 2016. PTB was defined as birth before 37 weeks of gestation. PTB was further classified into three clinically relevant groups to investigate the clinical heterogeneity of PTB: (a) preterm birth with premature rupture of membranes (PROM-PTB); (b) spontaneous preterm birth with intact membranes (S-PTB); and (c) medically-induced preterm birth (MI-PTB). The overall and sex-specific effect of IMH on PTB and various subtypes of PTB were estimated by using logistic regression in crude and adjusted models. Results: Pregnant women with IMH had an increased risk of PTB (odds ratio [OR]: 1.32 [95% confidence interval; CI: 1.02-1.70], p = 0.03) compared with women with euthyroid function. The increased risk of PTB is mainly driven by S-PTB (OR: 1.57 [CI: 1.11-2.24], p = 0.01), while women with early pregnancy IMH had no statistically significant increased risk of PROM-PTB and MI-PTB. The effect of IMH on PTB was modified by fetal sex (p-values for interaction = 0.04). More prominent effects were observed in women carrying a female fetus, while no statistically significant effects were found in women carrying a male fetus. Conclusions: This study revealed that pregnant women with IMH in early pregnancy have a higher risk of PTB compared with euthyroid women. The effect of IMH on PTB is mainly driven by S-PTB and is modified by fetal sex.

No association between subclinical hypothyroidism and dyslipidemia in children and adolescents

Background

There are controversies about the correlation between higher levels of thyroid stimulating hormone (TSH) and dyslipidemia in children. This study was designed to assess the relation between lipid profile components and TSH levels in children.

Method

This cross-sectional study was performed in a pediatric endocrinology growth assessment clinic in Shiraz, southern Iran. Children aged 2–18 years who referred to the clinic from January until April 2018 were included. TSH levels equal or above 5 mIU/L and lower than 10 mIU/L with normal free T4 (FT4) were considered as having subclinical hypothyroidism (SH).

Results

Six hundred sixty-six children were euthyroid while 181 had SH. No significant difference was found between the mean serum total cholesterol (P = 0.713), LDL-C (P = 0.369), HDL-C (P = 0.211), non-HDL-C (P = 0.929), and triglyceride (P = 0.215) levels between euthyroid children and subjects with SH. There was also no significant difference in the prevalence of dyslipidemias in any lipid profile components between the two groups. The adjusted correlation was not significant between TSH levels and any lipid profile component.

Conclusion

Based on the results of our study, we found no correlation between SH and dyslipidemia in children. The association between dyslipidemia and SH in children still seems to be inconsistent based on the results of this and previous studies. We recommend a meta-analysis or a significantly larger retrospective study on this subject.

Subclinical thyroid dysfunction in the first trimester of pregnancy: 'Disease' versus physiological (pulsatile) variation in TSH concentrations

BACKGROUND

There is no universal consensus regarding cut-off points for TSH in pregnancy, so concentrations of 2.5 or 4.0 mIU/L were suggested for first trimester (Endocrine Society [2012] and ATA [2017] guidelines, respectively). Yet, the impact of physiological variation in TSH secretion has not been assessed.

SUBJECTS AND METHODS

We assessed baseline concentrations of free T4, free T3 and TSH at 30-minute intervals (between 7.00 and 9.00 hours) in 110 healthy pregnant women, age 30.2 ± 6.0 years, 9.9 ± 2.4 weeks of gestation, and in 19 female controls, age 28.9 ± 10.7.

RESULTS

Mean TSH concentrations in pregnant women were 1.62 ± 1.26 mIU/L and on average varied by 39.5% (dispersion between the highest and the lowest TSH), with no difference in TSH variation between pregnant women and controls. Taking into account the highest TSH out of five consecutive measurements, TSH >2.5 mIU/L and TSH above 4.0 mIU/L were found in 23 (20.9%) and 10 (9.1%) pregnant women, respectively. In contrast, when the lowest TSH value was considered, then concentrations of TSH >2.5 mIU/L and >4.0 mIU/L were found in 14 (12.7%) and 4 (3.6%) women, respectively. This discrepancy was even more pronounced in aTPO-negative subjects (21 [21.2%] vs 8 [8.1%] women, for TSH >2.5 mIU/L, and six [6.06%] vs one [1.01%], for TSH >4.0 mIU/L). Furthermore, either six (5.4%) or 10 (9.1%) women had TSH concentrations below 0.1 mIU/L.

CONCLUSIONS

In a significant number of patients, diagnosis of subclinical thyroid dysfunction could be erroneously made not as a result of 'disease', but as a result of physiological variation in TSH concentrations.

Subclinical hypothyroidism in childhood, treatment or only follow-up?

Background

Subclinical hypothyroidism (SH) is defined as serum levels of thyroid-stimulating hormone (TSH) above the upper limit with normal concentrations of free T4 (fT4). Its management remains challenging. The aim of the study was to evaluate clinical and laboratory findings as well as the clinical course of children with SH followed in a third level hospital. Sixty-five patients aged between 2 and 18 years old were retrospectively studied.

Methods

The patients were followed for a median period of 9 months (range 6 months to 24 months). Those who normalized TSH levels were discharged (Group 1). If TSH persisted mildly elevated (5-10μUI/mL) with normal fT4 and negative TPOAb/TgAb, they were classified as Group 2 and followed semi-annually without treatment. Those patients whose TSH raised ≥10μUI/mL or who maintained TSH 5-10μUI/mL and positive TPOAb/TgAb were considered suitable for thyroxin therapy (Group 3, G3).

Results

In 89% of our patients, TSH concentrations spontaneously reverted to normality or remained stable without treatment (Groups 1 and 2), whereas less than 11% progressed to clinical hypothyroidism (Group 3). Baseline TSH was significantly lower in group 1 than in group 3. In group 3 the prevalence of female sex (71%) was higher and TPO antibodies were present in 85% of patients. The risk of developing overt hypothyroidism in patients with positive anti-thyroid antibodies respect to those who normalized TSH was 45 (95%CI 6.5–312.5).

Conclusion

Baseline TSH, female sex and the presence of thyroid autoimmunity were the best predictors of the evolution to SH over time.