Longitudinal study of serum thyroid hormone levels during normal pregnancy

Biomarkers of Postpartum Depression: A Narrative Review

Postpartum depression (PPD) is a disorder that impairs the formation of the relationship between mother and child, and reduces the quality of life for affected women to a functionally significant degree. Studying markers associated with PPD can help in early detection, prevention, or monitoring treatment. The purpose of this paper is to review biomarkers linked to PPD and to present selected theories on the pathogenesis of the disease based on data from biomarker studies. The complex etiology of the disorder reduces the specificity and sensitivity of markers, but they remain a valuable source of information to help clinicians. The biggest challenge of the future will be to translate high-tech methods for detecting markers associated with postpartum depression into more readily available and less costly ones. Population-based studies are needed to test the utility of potential PPD markers.

Management of overt hypothyroidism during pregnancy

Overt hypothyroidism is a common endocrine disorder affecting 1-2% of women of reproductive age. Optimizing treatment in pregnant women with overt hypothyroidism can reduce adverse fetal and maternal outcomes. Ideally, women who are known to have a history of hypothyroidism or those with risk factors for becoming hypothyroid, should have adequate preconception care to ensure euthyroidism from the onset of pregnancy, with a TSH target of below 2.5mIU/L. On women who are already on levothyroxine, an empirical dose increase of 30-50% as soon as pregnancy is confirmed may be considered. During pregnancy, levothyroxine doses should be titrated against TSH, which have trimester-specific ranges. In women who are known to be hypothyroid but are inadequately treated, we recommend a doubling of levothyroxine dose on at least three days a week to rapidly achieve euthyroidism. In newly diagnosed overt hypothyroidism in pregnancy, starting doses of either 100 or 150 mg daily may be considered safe.

Thyroid-stimulating hormone and risk of sudden cardiac death, total mortality and cardiovascular morbidity

BACKGROUND

Previous data on the association of thyroid function with total mortality, cardiovascular disease (CVD) outcomes and sudden cardiac death (SCD) are conflicting or limited. We investigated associations of thyroid-stimulating hormone (TSH) with these outcomes in a nationwide population-based prospective cohort study.

METHODS

We examined 5211 participants representative of the Finnish population aged ≥30 years in 2000-2001 and followed them for a median of 13.2 years. Using Cox proportional hazards regression models adjusted for baseline age, gender, smoking, diabetes, systolic blood pressure and total and high-density lipoprotein cholesterol, we assessed the associations of continuous baseline TSH and TSH categories (low [<0.4 mU/L], reference range [0.4-3.4 mU/L] and high [>3.4 mU/L]) with incident total mortality, SCD, coronary heart disease events, stroke, CVD, major adverse cardiac events and atrial fibrillation.

RESULTS

High TSH at baseline was related to a greater risk of total mortality (HR 1.34, 95% CI 1.02-1.76) and SCD (HR 2.28, 95% CI 1.13-4.60) compared with TSH within the reference range. High TSH was not associated with the other outcomes (P ≥ .51), whereas low TSH was not associated with any of the outcomes (P ≥ .09). TSH at baseline over the full range did not have a linear relation with any of the outcomes (P ≥ .17). TSH showed a U-shaped association with total mortality after a restricted cubic spline transformation (P = .01).

CONCLUSIONS

Thyroid function abnormalities could be linked with higher risks of total mortality and SCD. Large-scale randomized studies are needed for evidence-based recommendations regarding treatment of mild thyroid failure.

Association of thyroid-stimulating hormone with lipid concentrations: an 11-year longitudinal study

BACKGROUND

Scant data exist on the longitudinal association between thyroid function and lipid concentrations. We investigated associations of TSH and lipid concentrations cross-sectionally and longitudinally in a nationwide population sample.

METHODS

A total of 5205 randomly sampled participants representative of Finns aged ≥30 years were examined in 2000-2001 and included in cross-sectional analyses. A total of 2486 were re-examined 11 years later and included in longitudinal analyses. With linear regression models adjusted for age, gender, smoking and body mass index, we assessed the associations of baseline TSH and TSH categories (low, reference range and high) with total, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol; apolipoprotein A1 and B; and triglycerides at baseline and follow-up.

RESULTS

At baseline, higher TSH associated with higher total cholesterol (β = 0·025, standard error [SE] = 0·007, P < 0·001), LDL cholesterol (β = 0·020, SE = 0·007, P = 0·002), apolipoprotein B (β = 0·006, SE = 0·002, P < 0·001) and log triglycerides (β = 0·008, SE = 0·003, P = 0·004), but not with other lipid outcomes. Higher baseline TSH associated with higher total cholesterol (β = 0·056, SE = 0·026, P = 0·033), LDL cholesterol (β = 0·057, SE = 0·023, P = 0·015) and apolipoprotein B (β = 0·012, SE = 0·006, P = 0·028) at follow-up in women, but not with any lipid outcomes in men. Participants with high TSH at baseline had a 0·22 mmol/l (95% confidence interval 0·02-0·41 mmol/l) higher LDL cholesterol at follow-up (P = 0·028) than participants with TSH in the reference range (0·4-3·4 mU/l). However, exclusion of participants with high-risk baseline lipid values rendered these positive longitudinal associations nonsignificant (P ≥ 0·098).

CONCLUSIONS

We could confirm a modest association between higher TSH and an adverse lipid profile cross-sectionally but not indisputably longitudinally.

Association between thyroid-stimulating hormone and blood pressure in adults: an 11-year longitudinal study

BACKGROUND

The results of longitudinal studies on the association between thyroid function and blood pressure (BP) are divided. This study aimed to investigate this association in cross-sectional and longitudinal settings in a nationwide, random sample representative of the Finnish adult population aged 30 and over.

METHODS

The study sample was randomly drawn from the population register. A total of 5655 participants were included in the baseline analyses and 3453 in the 11-year prospective analyses. The associations between baseline TSH and (i) BP and BP change over time; and (ii) prevalent and incident hypertension were assessed using linear and logistic models, adjusted for age, gender, smoking and body mass index.

RESULTS

A positive association (β ± standard error) was observed between TSH and diastolic (0·36 ± 0·12, P = 0·003) but not systolic BP (0·16 ± 0·21, P = 0·45) at baseline. TSH was negatively associated with 11-year BP change in men (systolic: -0·92 ± 0·41, P = 0·03; diastolic: -0·66 ± 0·26, P = 0·01) but not in women (P ≥ 0·09 for systolic and diastolic BP change). Participants in the highest TSH tertile within the TSH reference interval (0·4-3·4 mU/L), as compared with the lowest, had increased odds of prevalent (odds ratio 1·22, 95% confidence interval 1·05-1·43, P = 0·01) but not incident hypertension (odds ratio 0·93, 95% confidence interval 0·73-1·19, P = 0·58).

CONCLUSIONS

A modest association was found between increasing TSH and prevalent but not incident hypertension. TSH was inversely associated with BP change in men in our study. These findings contest an independent role of thyroid function at normal to near-normal levels in the pathogenesis of hypertension.

Anti-thyroid peroxidase antibody positivity during early pregnancy is associated with pregnancy complications and maternal morbidity in later life

AIMS

We assessed the impact of detecting anti-thyroid peroxidase antibodies (anti-TPO-Ab) in the first trimester of pregnancy on pregnancy outcomes and maternal thyroid function during the postpartum period.

MATERIALS AND METHODS

In a prospective study consisting 400 pregnant women (8-12 weeks pregnant) were screened for their thyroid profile and followed-up to 12 weeks postpartum. Patients with abnormal thyroid function at 12 weeks postpartum were further followed-up with repeated assessment of thyroid stimulating hormone (TSH) and serum-free thyroxine-4 levels at 8 weeks interval up to 12 months postpartum.

RESULTS

11.5% of the subjects were positive for anti-TPO-Ab who had mean TSH level of 2.31 μIU/ml, which was significantly (P- 0.0001) higher than pregnant women negative for anti-TPO-Ab (1.73 μIU/ml). Increased incidence of miscarriage was observed in anti-TPO positive mothers when compared to antibody negative mothers. Postpartum thyroid dysfunction developed in 4.7% cases at 12 weeks, among them antibody positivity was observed in 81.25% of subjects. In 18.75% mothers positive for anti-TPO-Ab, the thyroid dysfunction persisted up to 12 months postpartum.

CONCLUSIONS

Thyroid antibodies detected in early pregnancy seems to be predicting pregnancy complications and later maternal thyroid disease related morbidity.

Thyroid-stimulating hormone reference range and factors affecting it in a nationwide random sample

BACKGROUND

Previous studies with mainly selected populations have proposed contradicting reference ranges for thyroid-stimulating hormone (TSH) and have disagreed on how screening, age and gender affect them. This study aimed to determine a TSH reference range on the Abbott Architect ci8200 integrated system in a large, nationwide, stratified random sample. To our knowledge this is the only study apart from the NHANES III that has addressed this issue in a similar nationwide setting. The effects of age, gender, thyroid peroxidase antibody (TPOAb)-positivity and medications on TSH reference range were also assessed.

METHODS

TSH was measured from 6247 participants randomly drawn from the population register to represent the Finnish adult population. TSH reference ranges were established of a thyroid-healthy population and its subpopulations with increasing and cumulative rigour of screening: screening for overt thyroid disease (thyroid-healthy population, n=5709); screening for TPOAb-positivity (risk factor-free subpopulation, n=4586); and screening for use of any medications (reference subpopulation, n=1849).

RESULTS

The TSH reference ranges of the thyroid-healthy population, and the risk factor-free and reference subpopulations were 0.4-4.4, 0.4-3.7 and 0.4-3.4 mU/L (2.5th-97.5th percentiles), respectively. Although the differences in TSH between subgroups for age (p=0.002) and gender (p=0.005) reached statistical significance, the TSH distribution curves of the subgroups were practically superimposed.

CONCLUSIONS

We propose 0.4-3.4 mU/L as a TSH reference range for adults for this platform, which is lower than those presently used in most laboratories. Our findings suggest that intensive screening for thyroid risk factors, especially for TPOAb-positivity, decreases the TSH upper reference limit.

Hazards associated with pregnancies and deliveries in lysinuric protein intolerance

Lysinuric protein intolerance (LPI) is an autosomal recessive transport disorder of the dibasic amino acids. The defect leads to deficiency of lysine, arginine, and ornithine and, secondarily, to a functional disorder of the urea cycle. Transient postprandial hyperammonemia and subsequent persistent protein aversion, linked with several other biochemical and clinical characteristics of the disease, suggest an increased risk for maternal and fetal complications during pregnancy and delivery. Our unique material on the outcomes of 18 pregnancies of 9 Finnish mothers with LPI and the follow-up of their 19 children shows that maternal LPI is truly associated with increased risk of anemia, toxemia, and intrauterine growth retardation during pregnancy and bleeding complications during delivery. Successful pregnancies and deliveries can still be achieved with careful follow-up of blood pressure and laboratory values. The children of the mothers with LPI generally develop normally. Special care of maternal protein nutrition and control of ammonemia, anemia, and toxemia during pregnancy are essential. We propose centralization of deliveries to obstetric units with capability to deal with bleeding complications and rare inborn errors of metabolism.

Investigations of thyroid hormones and antibodies based on a community health survey: the Busselton thyroid study

OBJECTIVE

Overt or subclinical thyroid dysfunction is common within the community, yet the significance of subtle anomalies in thyroid function tests remains contentious. The aims of this study were to: (a) establish reference intervals for serum-free thyroxine (FT4), thyroid-stimulating hormone (TSH) and thyroid antibodies (antithyroperoxidase, TPOAb and antithyroglobulin, TgAb) in the Busselton community of south-western Western Australia; and (b) determine the prevalence of thyroid hormone anomalies in this community.

SUBJECTS AND DESIGN

In 1981, 2115 adults residing in Busselton participated in a cross-sectional health survey that involved blood collection and a questionnaire on lifestyle and general health history.

MEASUREMENTS

Serum samples were analysed for FT4, TSH, TPOAb and TgAb by immunochemiluminescent assays.

RESULTS

Based on standard statistical approaches and using guidelines recommended by the National Academy of Clinical Biochemistry (NACB), reference intervals were derived for each analyte: 9-23 pmol/l for FT4, 0.4-4.0 mIU/l (TSH), < 35 KIU/l (TPOAb) and < 55 KIU/l (TgAb). The prevalence of elevated thyroid antibodies was 12.4% among subjects without a history of thyroid disease and is more common in women than in men. Elevated thyroid antibody levels were observed at both extremes of TSH abnormality, but were more commonly increased when TSH levels were above 4.0 mIU/l (63% subjects) than for those with TSH levels 0.4-4.0 mIU/l (7.8% subjects).

CONCLUSIONS

This study establishes the prevalence of antibodies to thyroperoxidase and thyroglobulin in a community-based sample and reference intervals for free T4 and TSH. When the NACB decision limits are applied to older men or women, there is a markedly increased number with 'elevated' autoantibody levels compared to sex- and age-specific reference intervals.

Outcomes of pregnancy complicated by thyroid disease

AIMS

To perform a case note review of pregnancies complicated by thyroid dysfunction to determine management and therapeutic intervention in relation to pregnancy outcome.

METHODS

A retrospective case note analysis of 81 ongoing pregnancies in 70 pregnant women with a history of thyroid dysfunction over a period of 5 years at the Glasgow Royal Maternity Hospital (GRMH), Glasgow, Scotland, United Kingdom. The results of thyroid function tests and whether a change in treatment was instituted were recorded. Thyroid function was assessed by standard laboratory reference ranges for free thyroxine (FT4) and thyroid stimulating hormone (TSH) in all trimesters. Other parameters were also noted.

RESULTS

Medication levels needed to be increased in the hypothyroid group (45%), and decreased (38%) in the hyperthyroid group.

CONCLUSION

Pregnancy outcome was good in majority of cases given appropriate replacement therapy for stated reference values.

Definição de valores normais de tiroxina livre durante a gravidez

A gravidez é acompanhada por uma série de modificações fisiológicas que incluem uma elevação significativa da globulina ligadora de tiroxina (Thyroxine-Binding Globulin, TBG). Tal elevação interfere nos níveis séricos totais da tiroxina (T4) e corrobora a utilização da medida de tiroxina livre (T4L), em conjunto com a dosagem de TSH, como métodos de primeira linha para a avaliação de função tiroidiana na gravidez. Uma definição cuidadosa dos valores normais de T4L durante a gestação é fundamental para o estudo de alterações da função tiroidiana, desde que disfunções mínimas podem resultar em anormalidades fetais significativas. Estudamos 132 grávidas normais, entre 6 e 38 semanas de gestação, e os resultados da medida de T4L por método indireto em duas etapas (valores normais de 0,7 a 1,5ng/dL em não grávidas, n= 797) mostraram valores entre 0,5 e 1,3ng/dL, com média±DP de 0,78±0,16ng/dL, significativamente mais baixos que os observados em não grávidas (0,98±0,14ng/dL, P<0,0001). Estes valores tendem a cair progressivamente ao longo da gestação, observando-se uma correlação negativa significativa com os níveis de TBG (rs= -0,51, P<0,0001), e com a idade gestacional (rs= -0,649, P<0,0001). Os níveis de TSH não mostraram correlação com a idade gestacional. Nossos dados comprovam a necessidade de definição mais rigorosa dos valores normais para T4L em mulheres grávidas, objetivando uma avaliação laboratorial mais precisa no diagnóstico e acompanhamento de disfunções tiroidianas nesse grupo de pacientes.

Interaction of estrogen therapy and thyroid hormone replacement in postmenopausal women

Based on the use of estrogen therapy/hormone therapy (ET/HT) in postmenopausal women and the prevalence of hypothyroidism in this population, it is estimated that approximately 5% of all postmenopausal women receive treatment with both ET/HT and thyroid hormone replacement. Hormone therapy generally refers to the combined use of estrogens and progestins, the latter administered on a continuous or intermittent basis. HT is indicated for the treatment of postmenopausal women with intact uteri, whereas ET is used in women who have had hysterectomies. Because of its hepatic first-pass effect, oral estrogen therapy, the most commonly used modality of ET/HT, raises the circulating levels of thyroxine-binding globulin (TBG), thereby increasing the bound fraction and decreasing the free (bioactive) fraction of circulating thyroxine (T(4)). As a consequence, oral ET/HT may increase the T(4) dosage requirements of women being treated for primary hypothyroidism as well as alter the pituitary-thyroid axis in euthyroid women. This paper reviews the potential interaction between ET/HT and thyroid hormone replacement based on the prevalence of their concomitant use, mechanistic aspects of the interaction, and recent clinical studies of the effects of oral ET in euthyroid and hypothyroid women. Other agents known to interact with thyroid hormone replacement, including soy supplements, are also reviewed. Because transdermal ET does not affect TBG levels and would not be expected to alter thyroid function, it may be a preferable modality for postmenopausal women who require concomitant treatment with ET/HT and T(4).

Endocrine factors in the etiology of postpartum depression

This article reviews the literature regarding endocrine factors postulated or presumed to be relevant in postpartum depression (PPD), a condition affecting at least 10% of childbearing women. The phenomenology and epidemiology of PPD are also described. Data suggest that parturition-related endocrine changes are causally implicated in PPD in a vulnerable subgroup of women. More specifically, studies by our group and others suggest a role for changes in estradiol and progesterone in precipitating mood symptoms among women with PPD. The mechanisms underlying such differential sensitivities remain undetermined. Future directions for research are explored.

Thyroid profile modifications during oral hormone replacement therapy in postmenopausal women

There are few data available about changes in thyroid hormone profiles after hormone replacement therapy (HRT). We analyzed the effect of two different oral estrogens/progestins (E/P) associations on thyroid hormones and thyroxine-binding globulin (TBG) levels in 14 postmenopausal normal women distributed at random into two groups. Both groups received daily for a year 2 mg of estradiol valeriante per os. In Group A (n = 7), estrogen was associated with norethisterone acetate. In Group B, estrogen was associated with promegestone in a similar schedule to Group A. Blood samples were withdrawn to measure estradiol (E2), thyroxine (T4), triiodothyronine (T3), free T4 (fT4), thyroid-stimulating hormone (TSH) and TBG before and after 3, 6 and 12 months of treatment. Estradiol level increased significantly in both groups, being higher in Group A than in B. Under therapy, T4 and TBG levels were increased in both groups, but within the normal range. T4 mean level increased by 34% in Group A and 20% in Group B. TBG increment was slightly significant for Group A (p < 0.02); with only a trend in Group B (p = 0.08). T3, fT4 and TSH levels did not change significantly and remained within the normal range. Oral therapy with associated E/P produces moderate increases in T4 and TBG levels. Our results suggest that in postmenopausal women on oral HRT, fT4 and TSH levels are the most useful tools to evaluate the thyroid axis status.