Previous cancers in women diagnosed with premature ovarian insufficiency: A nationwide population-based case-control study

INTRODUCTION

To investigate the occurrence of previous cancer diagnoses in women suffering from premature ovarian insufficiency (POI) and compare it with the general population, shedding light on the association between cancer, cancer treatments, and POI.

MATERIAL AND METHODS

We conducted a nationwide case-control study based on registry data from various sources, including the Social Insurance Institution, Finnish Population Information System, and Finnish Cancer Registry spanning from 1953 to 2018. Our participants comprised all women in Finland who, between 1988 and 2017, received hormone replacement therapy reimbursement for ovarian insufficiency before the age of 40 years (n = 5221). Controls, matched in terms of age and municipality of residence, were selected from the Finnish Population Information System (n = 20 822). Our main exposure variable was a history of cancer diagnosis preceding the diagnosis of POI. We analyzed odds ratios (OR) to compare the prevalence of previous cancers in women with POI with that in controls, stratifying results based on cancer type, age at cancer diagnosis, and the time interval between cancer diagnosis and POI. We also assessed changes in OR for previous cancer diagnoses over the follow-up period.

RESULTS

Out of the women diagnosed with POI, 21.9% had previously been diagnosed with cancer, resulting in an elevated OR of 36.5 (95% confidence interval [CI] 30.9 to 43.3) compared with 0.8% of the controls. The risk of developing POI was most pronounced during the first 2 years following a cancer diagnosis, with an OR of 103 (95% CI 74.1 to 144). Importantly, this risk remained elevated even when the time interval between cancer and POI exceeded 10 years, with an OR of 5.40 (95% CI 3.54 to 8.23).

CONCLUSIONS

This study reveals that 21.9% of women with POI have a history of cancer, making the prevalence of cancer among these women 27.5 times higher than age-matched controls in the Finnish population. The risk of developing POI is most substantial in the first 2 years following a cancer diagnosis. These findings underscore the role of cancer treatments as an etiological factor for POI and emphasize the importance of recognizing the risk of POI in cancer survivors for early diagnosis and intervention.

Risk Factors for Thyroid Dysfunction in Pregnancy: An Individual Participant Data Meta-Analysis

Background: International guidelines recommend targeted screening to identify gestational thyroid dysfunction. However, currently used risk factors have questionable discriminative ability. We quantified the risk for thyroid function test abnormalities for a subset of risk factors currently used in international guidelines. Methods: We included prospective cohort studies with data on gestational maternal thyroid function and potential risk factors (maternal age, body mass index [BMI], parity, smoking status, pregnancy through in vitro fertilization, twin pregnancy, gestational age, maternal education, and thyroid peroxidase antibody [TPOAb] or thyroglobulin antibody [TgAb] positivity). Exclusion criteria were pre-existing thyroid disease and use of thyroid interfering medication. We analyzed individual participant data using mixed-effects regression models. Primary outcomes were overt and subclinical hypothyroidism and a treatment indication (defined as overt hypothyroidism, subclinical hypothyroidism with thyrotropin >10 mU/L, or subclinical hypothyroidism with TPOAb positivity). Results: The study population comprised 65,559 participants in 25 cohorts. The screening rate in cohorts using risk factors currently recommended (age >30 years, parity ≥2, BMI ≥40) was 58%, with a detection rate for overt and subclinical hypothyroidism of 59%. The absolute risk for overt or subclinical hypothyroidism varied <2% over the full range of age and BMI and for any parity. Receiver operating characteristic curves, fitted using maternal age, BMI, smoking status, parity, and gestational age at blood sampling as explanatory variables, yielded areas under the curve ranging from 0.58 to 0.63 for the primary outcomes. TPOAbs/TgAbs positivity was associated with overt hypothyroidism (approximate risk for antibody negativity 0.1%, isolated TgAb positivity 2.4%, isolated TPOAb positivity 3.8%, combined antibody positivity 7.0%; p < 0.001), subclinical hypothyroidism (risk for antibody negativity 2.2%, isolated TgAb positivity 8.1%, isolated TPOAb positivity 14.2%, combined antibody positivity 20.0%; p < 0.001) and a treatment indication (risk for antibody negativity 0.2%, isolated TgAb positivity 2.2%, isolated TPOAb positivity 3.0%, and combined antibody positivity 5.1%; p < 0.001). Twin pregnancy was associated with a higher risk of overt hyperthyroidism (5.6% vs. 0.7%; p < 0.001). Conclusions: The risk factors assessed in this study had poor predictive ability for detecting thyroid function test abnormalities, questioning their clinical usability for targeted screening. As expected, TPOAb positivity (used as a benchmark) was a relevant risk factor for (subclinical) hypothyroidism. These results provide insights into different risk factors for gestational thyroid dysfunction.

Association of Gestational Free and Total Triiodothyronine With Gestational Hypertension, Preeclampsia, Preterm Birth, and Birth Weight: An Individual Participant Data Meta-analysis

CONTEXT

Triiodothyronine (T3) is the bioactive form of thyroid hormone. In contrast to thyroid-stimulating hormone and free thyroxine, we lack knowledge on the association of gestational T3 with adverse obstetric outcomes.

OBJECTIVE

To investigate the associaiton of gestational free or total T3 (FT3 or TT3) with adverse obstetric outcomes.

METHODS

We collected individual participant data from prospective cohort studies on gestational FT3 or TT3, adverse obstetric outcomes (preeclampsia, gestational hypertension, preterm birth and very preterm birth, small for gestational age [SGA], and large for gestational age [LGA]), and potential confounders. We used mixed-effects regression models adjusting for potential confounders.

RESULTS

The final study population comprised 33 118 mother-child pairs of which 27 331 had data on FT3 and 16 164 on TT3. There was a U-shaped association of FT3 with preeclampsia (P = .0069) and a J-shaped association with the risk of gestational hypertension (P = .029). Higher TT3 was associated with a higher risk of gestational hypertension (OR per SD of TT3 1.20, 95% CI 1.08 to 1.33; P = .0007). A lower TT3 but not FT3 was associated with a higher risk of very preterm birth (OR 0.72, 95% CI 0.55 to 0.94; P = .018). TT3 but not FT3 was positively associated with birth weight (mean difference per 1 SD increase in TT3 12.8, 95% CI 6.5 to 19.1 g, P < .0001) but there was no association with SGA or LGA.

CONCLUSION

This study provides new insights on the association of gestational FT3 and TT3 with major adverse pregnancy outcomes that form the basis for future studies required to elucidate the effects of thyroid function on pregnancy outcomes. Based on the current study, routine FT3 or TT3 measurements for the assessment of thyroid function during pregnancy do not seem to be of added value in the risk assessment for adverse outcomes.

TSH and FT4 Reference Interval Recommendations and Prevalence of Gestational Thyroid Dysfunction: Quantification of Current Diagnostic Approaches

CONTEXT

Guidelines recommend use of population- and trimester-specific thyroid-stimulating hormone (TSH) and free thyroxine (FT4) reference intervals (RIs) in pregnancy. Since these are often unavailable, clinicians frequently rely on alternative diagnostic strategies. We sought to quantify the diagnostic consequences of current recommendations.

METHODS

We included cohorts participating in the Consortium on Thyroid and Pregnancy. Different approaches were used to define RIs: a TSH fixed upper limit of 4.0 mU/L (fixed limit approach), a fixed subtraction from the upper limit for TSH of 0.5 mU/L (subtraction approach) and using nonpregnancy RIs. Outcome measures were sensitivity and false discovery rate (FDR) of women for whom levothyroxine treatment was indicated and those for whom treatment would be considered according to international guidelines.

RESULTS

The study population comprised 52 496 participants from 18 cohorts. Compared with the use of trimester-specific RIs, alternative approaches had a low sensitivity (0.63-0.82) and high FDR (0.11-0.35) to detect women with a treatment indication or consideration. Sensitivity and FDR to detect a treatment indication in the first trimester were similar between the fixed limit, subtraction, and nonpregnancy approach (0.77-0.11 vs 0.74-0.16 vs 0.60-0.11). The diagnostic performance to detect overt hypothyroidism, isolated hypothyroxinemia, and (sub)clinical hyperthyroidism mainly varied between FT4 RI approaches, while the diagnostic performance to detect subclinical hypothyroidism varied between the applied TSH RI approaches.

CONCLUSION

Alternative approaches to define RIs for TSH and FT4 in pregnancy result in considerable overdiagnosis and underdiagnosis compared with population- and trimester-specific RIs. Additional strategies need to be explored to optimize identification of thyroid dysfunction during pregnancy.

Maternal Thyroid Function During Pregnancy and Offspring White Matter Microstructure in Early Adulthood: A Prospective Birth Cohort Study

Background: The fetus is fully dependent on maternal thyroid hormones until mid-gestation and suboptimal maternal thyroid function has been associated with alterations in the neurodevelopment of the offspring. We used maternal free thyroxine (fT4) and thyrotropin (TSH) levels in early gestation to study the association of maternal thyroid function during early pregnancy and offspring brain white matter (WM) integrity in early adulthood. Methods: Our study population consisted of a total of 292 mother-child pairs. Maternal fT4 and TSH were used as predictors and offspring multimodal imaging measures of fractional anisotropy, mean diffusivity, and magnetization transfer ratio (FA, MD, and MTR) as dependent variables. First, as Global analysis, all analyzed 14 WM tracts were studied simultaneously using linear-mixed effect models. Second, if a global effect was detected, a post hoc Tract-wise analysis was carried out using linear models individually in each WM tract. Study population was stratified by sex. Results: We found a positive association between maternal fT4 and offspring Global FA in males when adjusted for all maternal and offspring covariates (n = 114; β = 0.154; confidence interval = 0.045-0.263; p = 0.006). The finding was observed to be driven by multiple WM tracts, of which three projection fiber tracts and the forceps minor survived correcting for multiple comparisons in Tract-wise analysis. Conclusions: Maternal thyroid function in early pregnancy was observed to be associated with WM microstructure in male offspring in early adulthood. Our results suggest that maternal fT4 levels in early pregnancy may modulate axonal characteristics, with a long-term effect on offspring WM development.

Association of genetic disorders and congenital malformations with premature ovarian insufficiency: a nationwide register-based study

STUDY QUESTION

Are genetic disorders and congenital malformations associated with premature ovarian insufficiency (POI)?

SUMMARY ANSWER

A wide range of genetic disorder and congenital malformation diagnoses are associated with POI, especially early onset POI.

WHAT IS KNOWN ALREADY

POI is known to be associated with some genetic disorders, such as Turner syndrome and Fragile X premutation. Multiple genetic syndromes, such as ataxia teleangiectasia and galactosemia, have also been associated with an increased risk of POI, and many of these genetic syndromes manifest with various congenital malformations. In previous studies, a genetic aetiology has been found for 7-15% of POI cases.

STUDY DESIGN, SIZE, DURATION

This population-based study included 5011 women diagnosed with POI in 1988-2017. The data were collected from various national registries and covers women with POI nationwide.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We identified 5011 women diagnosed with POI from 1988 to 2017 from the drug reimbursement registry of the Social Insurance Institution of Finland. Women with surgical POI (bilateral oophorectomy for benign indications) were not included. We selected four population controls per woman with POI matched by month and year of birth and municipality of residence. Diagnostic codes for genetic disorders and congenital malformations (GD/CM) for the cases and controls were searched from the Hospital Discharge Register. Binary logistic regression was used to compare the odds for GD/CM among cases and controls. To minimize bias, for the statistical analyses, we excluded diagnoses which were reported <2 years prior to the index date.

MAIN RESULTS AND THE ROLE OF CHANCE

Of the women with POI, 15.9% (n = 797) had at least one diagnostic code for GD or CM. The odds ratio (OR) for Turner syndrome was 275 (95% CI 68.1-1110), and for other sex chromosome abnormalities, it was 12.7 (95% CI 4.1-39.1). For autosomal single gene disorders, the OR was 16.5 (95% CI 6.2-43.7). Women with POI had a higher odds of having a GD/CM diagnosis in all categories. The OR for GD/CM diagnoses was highest among the youngest POI patients (10-14 years old, OR 24.1, 95% CI 15.1-38.2). The odds of having POI were higher the more GD or CM diagnoses a woman had.

LIMITATIONS, REASONS FOR CAUTION

Some women with POI might not have sought help for their symptoms and therefore remain undiagnosed. Due to the register-based nature of our study, we did not have access to more specific genetic diagnoses than international classification of diseases offers.

WIDER IMPLICATIONS OF THE FINDINGS

GD/CM diagnoses were strongly associated with POI, especially when POI was diagnosed at a young age. The risk of POI was highest in women with multiple GD/CM diagnoses. Early onset POI can be a sign of underlying genetic disorder or congenital anomaly, and this should serve as a reminder for clinicians to consider further examinations. To avoid unnecessary delay in the diagnosis of POI and starting relevant hormone replacement therapy treatment, clinicians should be aware of these associations.

STUDY FUNDING/COMPETING INTEREST(S)

Oulu University Hospital financially supported this work. H.S. has received personal grants from the Finnish Menopause Society, Oulu Medical Research Foundation, and Finnish Research Foundation of Gynaecology and Obstetrics. S.S. has received grants from the Finnish Menopause Society, the Finnish Medical Foundation, and the Juho Vainio Foundation. None of the authors have any competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

TSH and FT4 Reference Intervals in Pregnancy: A Systematic Review and Individual Participant Data Meta-Analysis

CONTEXT

Interpretation of thyroid function tests during pregnancy is limited by the generalizability of reference intervals between cohorts due to inconsistent methodology.

OBJECTIVE

(1) To provide an overview of published reference intervals for thyrotropin (TSH) and free thyroxine (FT4) in pregnancy, (2) to assess the consequences of common methodological between-study differences by combining raw data from different cohorts.

METHODS

(1) Ovid MEDLINE, EMBASE, and Web of Science were searched until December 12, 2021. Studies were assessed in duplicate. (2) The individual participant data (IPD) meta-analysis was performed in participating cohorts in the Consortium on Thyroid and Pregnancy.

RESULTS

(1) Large between-study methodological differences were identified, 11 of 102 included studies were in accordance with current guidelines; (2) 22 cohorts involving 63 198 participants were included in the meta-analysis. Not excluding thyroid peroxidase antibody-positive participants led to a rise in the upper limits of TSH in all cohorts, especially in the first (mean +17.4%; range +1.6 to +30.3%) and second trimester (mean +9.8%; range +0.6 to +32.3%). The use of the 95th percentile led to considerable changes in upper limits, varying from -10.8% to -21.8% for TSH and -1.2% to -13.2% for FT4. All other additional exclusion criteria changed reference interval cut-offs by a maximum of 3.5%. Applying these findings to the 102 studies included in the systematic review, 48 studies could be used in a clinical setting.

CONCLUSION

We provide an overview of clinically relevant reference intervals for TSH and FT4 in pregnancy. The results of the meta-analysis indicate that future studies can adopt a simplified study setup without additional exclusion criteria.

Indications for intensive care unit treatment among neonates born to mothers with thyroid disease: A population-based cohort study

INTRODUCTION

Thyroid diseases in pregnancy are relatively common and are associated with adverse pregnancy and perinatal outcomes, increasing a neonate's risk of admission to the neonatal intensive care unit (NICU). The aim of this study was to evaluate the indications for increased risk of NICU admission among the neonates of hypothyroid and hyperthyroid mothers.

MATERIAL AND METHODS

The study data consisted of all singleton deliveries (n = 734 773) between 2004 and 2016 in Finland collected from the Finnish Medical Birth Register. The odds of NICU admission (with 95% confidence intervals) were compared between the neonates of hypothyroid or hyperthyroid mothers and of mothers without any thyroid diseases by specified neonatal characteristics and morbidities using logistic regression analysis. The studied neonatal characteristics were preterm birth (<37+0 gestational weeks), low birthweight (<2500 g), the rate of small- and large-for-gestational age infants, and eight disease-specific neonatal outcomes: asphyxia, respiratory distress syndrome, meconium aspiration syndrome, pneumothorax, cardiovascular problems, infections, jaundice and hypoglycemia.

RESULTS

The most common indications for NICU care were principally the same in the neonates of the mothers with and without thyroid disease: respiratory distress syndrome, infections, preterm birth, low birthweight and neonatal hypoglycemia. The preterm neonates, neonates with low birthweight, and large-for-gestational-age infants had increased odds of NICU admission if their mother had hypothyroidism. Also neonates with cardiovascular problems, jaundice or hypoglycemia associated with maternal diabetes had increased odds of NICU admissions if their mother had hypothyroidism. Further, the preterm neonates, large-for-gestational-age infants, and term infants with jaundice had increased odds of NICU admission if their mother had hyperthyroidism.

CONCLUSIONS

The most common indications for NICU care were similar for the neonates of the mothers with and without thyroid disease. However, the neonates of the mothers with thyroid diseases were more likely to need NICU care. The neonates of the mothers with thyroid diseases had higher odds of NICU treatment in cases of preterm birth, large for gestational age, and hypoglycemia.

Association of Thyroid Peroxidase Antibodies and Thyroglobulin Antibodies with Thyroid Function in Pregnancy: An Individual Participant Data Meta-Analysis

Objectives: Thyroid autoimmunity is common in pregnant women and associated with thyroid dysfunction and adverse obstetric outcomes. Most studies focus on thyroid peroxidase antibodies (TPOAbs) assessed by a negative-positive dichotomy and rarely take into account thyroglobulin antibodies (TgAbs). This study aimed at determining the association of TPOAbs and TgAbs, respectively, and interdependently, with maternal thyroid function. Methods: This was a meta-analysis of individual participant cross-sectional data from 20 cohorts in the Consortium on Thyroid and Pregnancy. Women with multiple pregnancy, pregnancy by assisted reproductive technology, history of thyroid disease, or use of thyroid interfering medication were excluded. Associations of (log2) TPOAbs and TgAbs (with/without mutual adjustment) with cohort-specific z-scores of (log2) thyrotropin (TSH), free triiodothyronine (fT3), total triiodothyronine (TT3), free thyroxine (fT4), total thyroxine (TT4), or triiodothyronine:thyroxine (T3:T4) ratio were evaluated in a linear mixed model. Results: In total, 51,138 women participated (51,094 had TPOAb-data and 27,874 had TgAb-data). Isolated TPOAb positivity was present in 4.1% [95% confidence interval, CI: 3.0 to 5.2], isolated TgAb positivity in 4.8% [CI: 2.9 to 6.6], and positivity for both antibodies in 4.7% [CI: 3.1 to 6.3]. Compared with antibody-negative women, TSH was higher in women with isolated TPOAb positivity (z-score increment 0.40, CI: 0.16 to 0.64) and TgAb positivity (0.21, CI: 0.10 to 0.32), but highest in those positive for both antibodies (0.54, CI: 0.36 to 0.71). There was a dose-response effect of higher TPOAb and TgAb concentrations with higher TSH (TSH z-score increment for TPOAbs 0.12, CI: 0.09 to 0.15, TgAbs 0.08, CI: 0.02 to 0.15). When adjusting analyses for the other antibody, only the association of TPOAbs remained statistically significant. A higher TPOAb concentration was associated with lower fT4 (p < 0.001) and higher T3:T4 ratio (0.09, CI: 0.03 to 0.14), however, the association with fT4 was not significant when adjusting for TgAbs (p = 0.16). Conclusions: This individual participant data meta-analysis demonstrated an increase in TSH with isolated TPOAb positivity and TgAb positivity, respectively, which was amplified for individuals positive for both antibodies. There was a dose-dependent association of TPOAbs, but not TgAbs, with TSH when adjusting for the other antibody. This supports current practice of using TPOAbs in initial laboratory testing of pregnant women suspected of autoimmune thyroid disease. However, studies on the differences between TPOAb- and TgAb-positive women are needed to fully understand the spectrum of phenotypes.

Incidence and familial risk of premature ovarian insufficiency in the Finnish female population

STUDY QUESTION

What is the incidence of premature ovarian insufficiency (POI), has the incidence of POI changed over time, and what is the risk of POI among relatives of POI women?

SUMMARY ANSWER

The incidence of POI increased among females aged 15-19 years from 2007 onwards and decreased in older age groups, and among relatives of women with POI the risk of POI is significantly increased.

WHAT IS KNOWN ALREADY

So far, there has been no good quality, nationwide studies of the incidence of POI. Early menopause has been associated with the elevated risk of early menopause among relatives, but the knowledge of the familial risk of POI is scarce. Lower socioeconomic status has been associated with lower age at natural menopause.

STUDY DESIGN, SIZE, DURATION

Population-based study with 5011 women diagnosed with POI in 1988-2017. The data were collected from national registries and covers POI subjects in entire Finland.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women with hormone replacement therapy reimbursement for POI were identified from Social Insurance Institution (SII). We calculated POI incidence in different age groups and studied the changes in the incidence rate over time in 5-year segments. Four population-based controls were selected from the Digital and Population Data Services Agency (DVV) for each POI woman. Family members of the POI cases and controls were identified from the DVV and linked to SII reimbursement data to identify POI diagnoses among them. The familial risk of POI was estimated with a logistical regression model.

MAIN RESULTS AND THE ROLE OF CHANCE

The incidence was highest in the 35-39 age group, ranging from 73.8/100 000 women-years in 1993-1997 to 39.9/100 000 women-years in 2013-2017. From 2007, the incidence among 15- to 19-year-olds rose from 7.0 to 10.0/100 000 women-years in 2015-2017. Cumulative incidence of POI for women under 40 years in 1988-2017 was 478/100 000 women. The relative risk of POI among relatives of women with POI was 4.6 (95% CI 3.3-6.5) compared to relatives of women without POI. POI women tended to have slightly lower socioeconomic status and level of education compared to controls.

LIMITATIONS, REASONS FOR CAUTION

For some women with POI, diagnosis or reimbursement may be lacking. However, we presume that these women represent a minority due to the nature of the disease and the economic benefits of reimbursement. Some changes in the incidence of POI can reflect changes in clinical practice and changing treatments and reimbursement criteria.

WIDER IMPLICATIONS OF THE FINDINGS

The risk of developing POI is significantly higher in women who have first-degree relatives diagnosed with POI. Raising awareness of the increased risk might lead to earlier diagnosis and initiation of hormonal replacement therapy, possibly preventing adverse effects of low oestrogen levels, such as osteoporosis.

STUDY FUNDING/COMPETING INTEREST(S)

This work was financially supported by the Oulu University Hospital. H.S. received a grant from Finnish Menopause Society. S.M.S. received a grant from the Finnish Menopause Society, the Finnish Medical Foundation and the Juho Vainio Foundation. The authors do not have any competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

Does climacteric status impact regulation of the autonomic nervous system at the age of 46 years?

OBJECTIVE

To investigate whether an earlier-onset climacteric phase is associated with autonomic imbalance at the age of 46 years.

METHODS

This cross-sectional birth cohort study included 2661 women aged 46 years. Participants were divided into climacteric (n = 359) and preclimacteric (n = 2302) groups based on menstrual history and follicle stimulating hormone values. The mean heart rate (HR), low-frequency (LF) power, high-frequency (HF) power and LF/HF ratio were analyzed from heart rate variability recordings. The variables were compared between the groups using multivariable linear regression models, including body mass index, smoking and physical activity. The effects of hormone therapy and hot flashes on autonomic function were evaluated in sub-analyses.

RESULTS

Climacteric women had a lower mean HR in seated (71.9 ± 10.5 vs. 72.6 ± 10.4 bpm, p = 0.015) and standing (81.2 ± 12.8 vs. 83.6 ± 12.1 bpm, p = 0.002) positions compared to preclimacteric women, and the differences remained significant after the adjustments. In the sub-analyses, more frequent hot flashes were associated with a lower LF power and LF/HF ratio in the sitting position.

CONCLUSIONS

The present study suggested an association between greater parasympathetic activation in women with more advanced climacteric status at the age of 46 years.

Association between maternal thyroid function and risk of gestational hypertension and pre-eclampsia: a systematic review and individual-participant data meta-analysis

BACKGROUND

Adequate maternal thyroid function is important for an uncomplicated pregnancy. Although multiple observational studies have evaluated the association between thyroid dysfunction and hypertensive disorders of pregnancy, the methods and definitions of abnormalities in thyroid function tests were heterogeneous, and the results were conflicting. We aimed to examine the association between abnormalities in thyroid function tests and risk of gestational hypertension and pre-eclampsia.

METHODS

In this systematic review and meta-analysis of individual-participant data, we searched MEDLINE (Ovid), Embase, Scopus, and the Cochrane Database of Systematic Reviews from date of inception to Dec 27, 2019, for prospective cohort studies with data on maternal concentrations of thyroid-stimulating hormone (TSH), free thyroxine (FT₄), thyroid peroxidase (TPO) antibodies, individually or in combination, as well as on gestational hypertension, pre-eclampsia, or both. We issued open invitations to study authors to participate in the Consortium on Thyroid and Pregnancy and to share the individual-participant data. We excluded participants who had pre-existing thyroid disease or multifetal pregnancy, or were taking medications that affect thyroid function. The primary outcomes were documented gestational hypertension and pre-eclampsia. Individual-participant data were analysed using logistic mixed-effects regression models adjusting for maternal age, BMI, smoking, parity, ethnicity, and gestational age at blood sampling. The study protocol was registered with PROSPERO, CRD42019128585.

FINDINGS

We identified 1539 published studies, of which 33 cohorts met the inclusion criteria and 19 cohorts were included after the authors agreed to participate. Our study population comprised 46 528 pregnant women, of whom 39 826 (85·6%) women had sufficient data (TSH and FT₄ concentrations and TPO antibody status) to be classified according to their thyroid function status. Of these women, 1275 (3·2%) had subclinical hypothyroidism, 933 (2·3%) had isolated hypothyroxinaemia, 619 (1·6%) had subclinical hyperthyroidism, and 337 (0·8%) had overt hyperthyroidism. Compared with euthyroidism, subclinical hypothyroidism was associated with a higher risk of pre-eclampsia (2·1% vs 3·6%; OR 1·53 [95% CI 1·09-2·15]). Subclinical hyperthyroidism, isolated hypothyroxinaemia, or TPO antibody positivity were not associated with gestational hypertension or pre-eclampsia. In continuous analyses, both a higher and a lower TSH concentration were associated with a higher risk of pre-eclampsia (p=0·0001). FT₄ concentrations were not associated with the outcomes measured.

INTERPRETATION

Compared with euthyroidism, subclinical hypothyroidism during pregnancy was associated with a higher risk of pre-eclampsia. There was a U-shaped association of TSH with pre-eclampsia. These results quantify the risks of gestational hypertension or pre-eclampsia in women with thyroid function test abnormalities, adding to the total body of evidence on the risk of adverse maternal and fetal outcomes of thyroid dysfunction during pregnancy. These findings have potential implications for defining the optimal treatment target in women treated with levothyroxine during pregnancy, which needs to be assessed in future interventional studies.

FUNDING

Arkansas Biosciences Institute and Netherlands Organization for Scientific Research.

Iodine and thyroid status during pregnancy and risk of stillbirth: A population-based nested case-control study

Prior research suggests that severe iodine deficiency in pregnancy may be associated with stillbirth. However, the relationship between mild to moderate iodine insufficiency, which is prevalent even in developed countries, and risk of stillbirth is unclear. We thus examined associations of iodine status and risk of stillbirth in a prospective population‐based nested case–control study in Finland, a mild to moderately iodine insufficient population. Stillbirth cases (n = 199) and unaffected controls (n = 249) were randomly selected from among all singleton births in Finland from 2012 to 2013. Serum samples were collected between 10 and 14 weeks gestation and analysed for iodide, thyroglobulin (Tg) and thyroid‐stimulating hormone (TSH). Odds ratios (ORs) and 95% confidence intervals (CIs) for stillbirth were estimated using logistic regression. After adjusting for maternal age, prepregnancy body mass index, socio‐economic status and other factors, neither high nor low serum iodide was associated with risk of stillbirth (Q1 vs. Q2–Q3 OR = 0.92, 95% CI = 0.78–1.09; Q4 vs. Q2–Q3 OR = 0.78; 95% CI = 0.45–1.33). Tg and TSH were also not associated with risk of stillbirth in adjusted models. Maternal iodine status was not associated with stillbirth risk in this mildly to moderately iodine‐deficient population. Tg and TSH, which reflect functional iodine status, were also not associated with stillbirth risk. The lack of associations observed between serum iodide, TSH and Tg and risk of stillbirth is reassuring, given that iodine deficiency in pregnancy is prevalent in developed countries.

The Joint Role of Iodine Status and Thyroid Function on Risk for Preeclampsia in Finnish Women: a Population-Based Nested Case-Control Study

Preeclampsia, a pregnancy disorder that includes hypertension and proteinuria, is a major cause of maternal and fetal morbidity and mortality. Some studies, but not all, have found that women with preeclampsia have significantly lower iodine levels than healthy pregnant women. Resolving this issue is important because iodine deficiency in pregnancy is common in the USA and parts of Europe including Finland. We conducted a nested case-control study to determine whether the risk for preeclampsia is associated with iodine status. We measured serum iodine, thyroglobulin (Tg), and thyroid stimulating hormone (TSH) at 10-14 weeks gestational age in 204 women with preeclampsia and 246 unaffected controls selected from all births in Finland. We found no significant difference in iodine (case mean = 26.04 ng/mL, control mean = 27.88 ng/mL, p = 0.995), Tg (case mean = 31.11 ng/mL, control mean = 29.61 ng/mL, p = 0.996), and TSH (case mean = 1.30 mIU/L, control mean = 1.24 mIU/L, p = 0.896) levels between cases and controls. There was no significant relationship between preeclampsia risk and iodine, Tg, or TSH after adjustment for known risk factors. These results are reassuring given the high prevalence of iodine deficiency in pregnancy.

The Increased Trend of Medical Treatment for Thyroid Diseases during Pregnancy: A 13-Year National Study

OBJECTIVE

Thyroid dysfunction affects up to 5-7% of all pregnancies. The rates of thyroid hormone use in nonpregnant population have substantially increased in recent years. The aim of this study was to assess possible changes in the use of levothyroxine substitution and antithyroid drugs over time in pregnant women.

METHODS

The study data consisted of all singleton pregnancies (N = 736,873) between 2004 and 2016 in Finland collected from the Finnish Medical Birth Register. The Prescription Register and Special Refund Entitlement Register provided information on levothyroxine and antithyroid drug purchases. The annual rates of levothyroxine and antithyroid drug prescription redemptions were explored to estimate changes in exposure rates to thyroid medication from 2004 to 2016. Joinpoint regression analyses were performed to explore interannual variability in levothyroxine and antithyroid drug treatment.

RESULTS

There was more than a five-fold increase in levothyroxine use during the study period; in 2004, 1.1% of pregnant women had levothyroxine treatment, and by 2016, the prevalence increased to 6.2%. In addition, we observed a slight increase in antithyroid medication during pregnancy, but antithyroid drug use during pregnancy overall was very rare. In 2004, 0.05% of pregnant women used antithyroid drugs, and by 2016, this percentage had increased to 0.14%.

CONCLUSIONS

Our study shows that the rate of levothyroxine use in pregnancy has markedly increased. This suggests that tracing and screening relevant patients and awareness of thyroid disorders on pregnancy and their significance for the pregnancy outcome have increased and the threshold to treat thyroid disorders has declined.

Maternal hyperthyroidism and pregnancy outcomes: A population-based cohort study

OBJECTIVE

Maternal hyperthyroidism and antithyroid medications have been associated with adverse pregnancy and perinatal outcomes. This nationwide register-based study investigated the association of maternal hyperthyroidism and antithyroid drug (ATD) use with pregnancy outcomes and included all singleton births in Finland between 2004 and 2013 (N = 571 785).

DESIGN, PATIENTS AND MEASUREMENTS

Hyperthyroid mothers were identified in the Medical Birth Register, and data on ATD use before and/or during pregnancy were collected from the Prescription Register. The odds ratios, with 95% confidence intervals, for adverse outcomes among hyperthyroid mothers and mothers without thyroid disease were compared using logistic regression.

RESULTS

In total, 2144 (0.37%) of all the women had diagnoses of hyperthyroidism, and 580 (27%) of these women had used ATDs before and/or during pregnancy. Compared to the mothers without thyroid disease, maternal hyperthyroidism was associated with older age, multiparity, smoking, previous miscarriages, and overweight or obesity. The mothers diagnosed with hyperthyroidism also had increased odds of gestational hypertensive disorders, caesarean sections, placental abruptions, preterm births, small-for-gestational-age newborns and neonatal intensive care unit treatment. The odds of pregnancy and/or perinatal complications were higher among those who had used ATDs (indicative of active disease), but those who had not received ATD treatment also had increased odds of such complications compared to the mothers without thyroid disease.

CONCLUSIONS

Women with active hyperthyroidism and those with histories of hyperthyroidism should be considered at risk of developing pregnancy and perinatal complications and should therefore be monitored during pregnancy.

Association of maternal thyroid function with birthweight: a systematic review and individual-participant data meta-analysis

BACKGROUND

Adequate transplacental passage of maternal thyroid hormone is important for normal fetal growth and development. Maternal overt hypothyroidism and hyperthyroidism are associated with low birthweight, but important knowledge gaps remain regarding the effect of subclinical thyroid function test abnormalities on birthweight-both in general and during the late second and third trimester of pregnancy. The aim of this study was to examine associations of maternal thyroid function with birthweight.

METHODS

In this systematic review and individual-participant data meta-analysis, we searched MEDLINE (Ovid), Embase, Web of Science, the Cochrane Central Register of Controlled Trials, and Google Scholar from inception to Oct 15, 2019, for prospective cohort studies with data on maternal thyroid function during pregnancy and birthweight, and we issued open invitations to identify study authors to join the Consortium on Thyroid and Pregnancy. We excluded participants with multiple pregnancies, in-vitro fertilisation, pre-existing thyroid disease or thyroid medication usage, miscarriages, and stillbirths. The main outcomes assessed were small for gestational age (SGA) neonates, large for gestational age neonates, and newborn birthweight. We analysed individual-participant data using mixed-effects regression models adjusting for maternal age, BMI, ethnicity, smoking, parity, gestational age at blood sampling, fetal sex, and gestational age at birth. The study protocol was pre-registered at the International Prospective Register of Systematic Reviews, CRD42016043496.

FINDINGS

We identified 2526 published reports, from which 36 cohorts met the inclusion criteria. The study authors for 15 of these cohorts agreed to participate, and five more unpublished datasets were added, giving a study population of 48 145 mother-child pairs after exclusions, of whom 1275 (3·1%) had subclinical hypothyroidism (increased thyroid stimulating hormone [TSH] with normal free thyroxine [FT4]) and 929 (2·2%) had isolated hypothyroxinaemia (decreased FT4 with normal TSH). Maternal subclinical hypothyroidism was associated with a higher risk of SGA than was euthyroidism (11·8% vs 10·0%; adjusted risk difference 2·43%, 95% CI 0·43 to 4·81; odds ratio [OR] 1·24, 1·04 to 1·48; p=0·015) and lower mean birthweight (mean difference -38 g, -61 to -15; p=0·0015), with a higher effect estimate for measurement in the third trimester than in the first or second. Isolated hypothyroxinaemia was associated with a lower risk of SGA than was euthyroidism (7·3% vs 10·0%, adjusted risk difference -2·91, -4·49 to -0·88; OR 0·70, 0·55 to 0·91; p=0·0073) and higher mean birthweight (mean difference 45 g, 18 to 73; p=0·0012). Each 1 SD increase in maternal TSH concentration was associated with a 6 g lower birthweight (-10 to -2; p=0·0030), with higher effect estimates in women who were thyroid peroxidase antibody positive than for women who were negative (pinteraction=0·10). Each 1 SD increase in FT4 concentration was associated with a 21 g lower birthweight (-25 to -17; p<0·0001), with a higher effect estimate for measurement in the third trimester than the first or second.

INTERPRETATION

Maternal subclinical hypothyroidism in pregnancy is associated with a higher risk of SGA and lower birthweight, whereas isolated hypothyroxinaemia is associated with lower risk of SGA and higher birthweight. There was an inverse, dose-response association of maternal TSH and FT4 (even within the normal range) with birthweight. These results advance our understanding of the complex relationships between maternal thyroid function and fetal outcomes, and they should prompt careful consideration of potential risks and benefits of levothyroxine therapy during pregnancy.

FUNDING

Netherlands Organization for Scientific Research (grant 401.16.020).

Association of Thyroid Function Test Abnormalities and Thyroid Autoimmunity With Preterm Birth: A Systematic Review and Meta-analysis

Importance

Maternal hypothyroidism and hyperthyroidism are risk factors for preterm birth. Milder thyroid function test abnormalities and thyroid autoimmunity are more prevalent, but it remains controversial if these are associated with preterm birth.

Objective

To study if maternal thyroid function test abnormalities and thyroid autoimmunity are risk factors for preterm birth.

Data Sources and Study Selection

Studies were identified through a search of the Ovid MEDLINE, EMBASE, Web of Science, the Cochrane Central Register of Controlled Trials, and Google Scholar databases from inception to March 18, 2018, and by publishing open invitations in relevant journals. Data sets from published and unpublished prospective cohort studies with data on thyroid function tests (thyrotropin [often referred to as thyroid-stimulating hormone or TSH] and free thyroxine [FT4] concentrations) or thyroid peroxidase (TPO) antibody measurements and gestational age at birth were screened for eligibility by 2 independent reviewers. Studies in which participants received treatment based on abnormal thyroid function tests were excluded.

Data Extraction and Synthesis

The primary authors provided individual participant data that were analyzed using mixed-effects models.

Main Outcomes and Measures

The primary outcome was preterm birth (<37 weeks' gestational age).

Results

From 2526 published reports, 35 cohorts were invited to participate. After the addition of 5 unpublished data sets, a total of 19 cohorts were included. The study population included 47 045 pregnant women (mean age, 29 years; median gestational age at blood sampling, 12.9 weeks), of whom 1234 (3.1%) had subclinical hypothyroidism (increased thyrotropin concentration with normal FT4 concentration), 904 (2.2%) had isolated hypothyroxinemia (decreased FT4 concentration with normal thyrotropin concentration), and 3043 (7.5%) were TPO antibody positive; 2357 (5.0%) had a preterm birth. The risk of preterm birth was higher for women with subclinical hypothyroidism than euthyroid women (6.1% vs 5.0%, respectively; absolute risk difference, 1.4% [95% CI, 0%-3.2%]; odds ratio [OR], 1.29 [95% CI, 1.01-1.64]). Among women with isolated hypothyroxinemia, the risk of preterm birth was 7.1% vs 5.0% in euthyroid women (absolute risk difference, 2.3% [95% CI, 0.6%-4.5%]; OR, 1.46 [95% CI, 1.12-1.90]). In continuous analyses, each 1-SD higher maternal thyrotropin concentration was associated with a higher risk of preterm birth (absolute risk difference, 0.2% [95% CI, 0%-0.4%] per 1 SD; OR, 1.04 [95% CI, 1.00-1.09] per 1 SD). Thyroid peroxidase antibody-positive women had a higher risk of preterm birth vs TPO antibody-negative women (6.6% vs 4.9%, respectively; absolute risk difference, 1.6% [95% CI, 0.7%-2.8%]; OR, 1.33 [95% CI, 1.15-1.56]).

Conclusions and Relevance

Among pregnant women without overt thyroid disease, subclinical hypothyroidism, isolated hypothyroxinemia, and TPO antibody positivity were significantly associated with higher risk of preterm birth. These results provide insights toward optimizing clinical decision-making strategies that should consider the potential harms and benefits of screening programs and levothyroxine treatment during pregnancy.

Climacteric Status at the Age of 46: Impact on Metabolic Outcomes in Population-Based Study

CONTEXT

Menopausal transition is associated with increased cardiovascular risks. Available data on the effect of earlier climacterium on these risks are limited.

OBJECTIVE

To compare cardiovascular risk-associated parameters at the ages of 14, 31, and 46 in relation to climacteric status at the age of 46.

DESIGN, SETTING, AND PARTICIPANTS

A prospective cohort study including 2685 women from the Northern Finland Birth Cohort 1966.

MAIN OUTCOME MEASURES

Follicle-stimulating hormone, body mass index (BMI), waist circumference, waist-to-hip ratio (WHR), blood pressure (BP), body composition, cholesterol levels, testosterone (T) levels, free androgen index (FAI), high-sensitivity C-reactive protein (hs-CRP), and liver enzymes.

RESULTS

Women who were climacteric at the age of 46 had lower BMIs (P = 0.029), T levels (P = 0.018), and FAIs (P = 0.009) at the age of 31. At the age of 46, they had less skeletal muscle (P < 0.001), a higher fat percentage (P = 0.016), higher cholesterol levels [total cholesterol (P < 0.001), low-density lipoprotein cholesterol (P < 0.001), high-density lipoprotein cholesterol (HDL-C; P = 0.022), and triglycerides (P = 0.008)], and higher alanine aminotransferase (P = 0.023) and γ-glutamyltransferase (P < 0.001) levels compared with preclimacteric women. Waist circumference, WHR, BP, and hs-CRP levels did not differ between the groups. Of the climacteric women, 111/381 were using hormone-replacement therapy (HRT). In subanalysis that excluded the HRT users, triglycerides, HDL-C, and body fat percentage did not differ among the groups.

CONCLUSIONS

Earlier climacterium is associated with mainly unfavorable metabolic changes.

The joint role of thyroid function and iodine concentration on gestational diabetes risk in a population-based study

INTRODUCTION

Iodine is essential for thyroid function, and iodine deficiency during pregnancy is common in Europe and the USA. However, no published studies have examined the role of iodine deficiency in the relation between thyroid function and gestational diabetes mellitus (GDM).

MATERIAL AND METHODS

We conducted a population-based, nested case-control study within the Finnish Maternity Cohort using pregnancy and perinatal outcome data from the Finnish Maternal Birth Register. We randomly selected 224 GDM cases with singleton pregnancies and 224 controls without GDM from all singleton births occurring in Finland during 2012-2013. Blood was drawn at 10-14 weeks' gestation and analyzed for serum iodide, thyroglobulin, and thyroid-stimulating hormone (TSH) concentrations. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CI) of GDM.

RESULTS

Very high thyroglobulin concentration (>95% percentile; >83 μg/L) was not associated with significantly altered odds of GDM compared to those with normal levels (OR 0.41; 95% CI: 0.12, 1.38). High concentrations of TSH were also not associated with increased odds of GDM compared to normal levels of TSH (OR 0.45; 95% CI: 0.06, 3.18). Women in the lowest 5th percentile (<1.58 ng/mL) of iodine did not have increased odds of GDM compared to those with iodide in the highest quartile (OR 0.39; 95% CI: 0.11, 1.35).

CONCLUSIONS

Low levels of iodide and thyroid function in early pregnancy are not associated with increased risk of GDM in this mildly iodine-deficient population.

Pregnancy and Perinatal Outcome Among Hypothyroid Mothers: A Population-Based Cohort Study

BACKGROUND

Maternal hypothyroidism has been associated with adverse pregnancy outcomes. A large nationwide register-based cohort with data on medication purchases was established to study the associations between maternal hypothyroidism, levothyroxine (LT4) use, and pregnancy and perinatal complications.

METHODS

The data included all singleton births between 2004 and 2013 (N = 571,785) in Finland. Hypothyroid mothers (n = 16,364) were identified in the Finnish Medical Birth Register. Of these women, 95.8% used LT4 medication, and 37.5% had consistent LT4 use during pregnancy. Hypothyroid mothers were compared to mothers without thyroid disease (N = 550,860) using logistic regression. The main outcome measures were pregnancy and perinatal complications.

RESULTS

Maternal hypothyroidism was associated with several pregnancy and perinatal complications, including gestational diabetes mellitus (odds ratio [OR] = 1.19 [confidence interval (CI) 1.13-1.25]), gestational hypertension (OR = 1.20 [CI 1.10-1.30]), severe preeclampsia (OR = 1.38 [CI 1.15-1.65]), cesarean section (OR = 1.22 [CI 1.17-1.27]), preterm births (OR = 1.25 [CI 1.16-1.34]), large-for-gestational age newborns (OR = 1.30 [CI 1.19-1.42]), major congenital anomalies (OR = 1.14 [CI 1.06-1.22]), and neonatal intensive care unit admission (OR = 1.23 [CI 1.17-1.29]). However, among mothers with consistent LT4 purchases, only the associations between gestational diabetes mellitus (OR = 1.12 [CI 1.03-1.22]), cesarean section (OR = 1.13 [CI 1.06-1.21]), neonatal intensive care unit admission (OR = 1.09 [CI 1.01-1.29]), and large-for-gestational age newborns (OR = 1.26 [CI 1.10-1.45]) and maternal hypothyroidism remained.

CONCLUSIONS

Maternal hypothyroidism is associated with several pregnancy and perinatal complications, but consistent LT4 use may reduce many of the risks.

Maternal Thyroid Function During Pregnancy and the Child's Linguistic and Sensory Development in the Northern Finland Birth Cohort 1986

BACKGROUND

Maternal hypothyroidism and hypothyroxinemia are associated with poor neuropsychological development in children. Previous research is lacking on whether maternal thyroid dysfunction affects sensory and linguistic development in childhood.

METHODS

The Northern Finland Birth Cohort 1986 included all births within a year (9,362 women, 9,479 children) from the two northernmost Finnish provinces. Maternal serum samples (n = 5,791) were obtained in early pregnancy and analyzed for TSH, free T4, and thyroid peroxidase antibodies (TPO-Abs). Five thousand three hundred and ninety-one parents evaluated their child's sensory and linguistic development at 7 years old via a questionnaire (excluding children with an intelligence quotient ≤85). The prevalence of sensory and linguistic impairments was compared between mothers with and without thyroid dysfunction.

RESULTS

There were no statistically significant differences in the prevalence of sensory or linguistic impairment between children of mothers with and without thyroid dysfunction. Children of hypothyroid and hypothyroxinemic mothers had an increased prevalence of vision impairment compared with those of euthyroid mothers (10.8 and 11.7%, respectively, versus 6.5%), but the difference was not significant. All results remained similar after excluding TPO-Ab-positive mothers and premature children.

CONCLUSION

We did not find an association between maternal thyroid dysfunction during pregnancy and sensory and linguistic development impairment in childhood. A somewhat higher prevalence of vision impairment was seen in children of hypothyroid and hypothyroxinemic mothers, which merits further research.

Maternal Thyroid Antibodies Associates With Cardiometabolic Risk Factors in Children at the Age of 16

CONTEXT AND OBJECTIVE

The objective of this study was to determine the effects of maternal thyroid dysfunction or antibodies during pregnancy on the cardiometabolic risk factors in children.

DESIGN, SETTING, AND PARTICIPANTS

This prospective population-based cohort study, Northern Finland Birth Cohort 1986, included all pregnancies within a year in the area. Maternal serum samples were collected before the 20th week of gestation and analyzed for thyrotropin, free T4, thyroid-peroxidase antibodies (TPO-Abs), and thyroglobulin antibodies (Tg-Abs). Cardiometabolic risk factors in children at the age of 16 years were evaluated via blood sampling and clinical examination. Data were available for 3229 to 4176 mother-child pairs.

MAIN OUTCOME MEASURES

Waist circumference, blood pressure, lipids and lipoproteins, and insulin resistance were measured. Odds ratios (ORs) with 95% confidence intervals (CIs) of cardiometabolic risk factors in children with and without mothers with thyroid dysfunction or antibodies were calculated with logistic regression and adjusted for covariates.

RESULTS

Children of TPO-Ab-positive mothers had higher odds of metabolic syndrome (OR, 2.57; 95%, CI 1.26 to 5.25) and waist circumference indicative of metabolic syndrome (OR, 1.69; 95% CI, 1.14 to 2.50). They were also more likely to be overweight or obese (OR, 1.56; 95% CI, 1.04 to 2.34). Maternal thyroid dysfunction or Tg-Ab positivity did not associate with cardiometabolic risk factors in children.

CONCLUSION

Metabolic syndrome, greater waist circumference, and higher body mass index were more prevalent in children of TPO-Ab-positive mothers, indicating an adverse cardiovascular health profile.

Maternal and Child's Thyroid Function and Child's Intellect and Scholastic Performance

BACKGROUND

Maternal hypothyroidism and/or hypothyroxinemia have been associated with child's poor neuropsychological development, but the results have been inconsistent.

METHODS

The Northern Finland Birth Cohort 1986 included all expected births within a year (9362 women, 9479 children) from the two northernmost provinces of Finland. Maternal serum samples (n = 5791) were obtained in early pregnancy (M ± SD = 10.7 ± 2.8 weeks' gestation), and serum samples from their children were obtained at 16 years of age (n = 5829). All samples were analyzed for thyrotropin, free thyroxine (fT4), and thyroid peroxidase antibodies. The children's school performance was evaluated by their main teachers at eight years of age, as well as by the adolescents themselves at 16 years of age. Data on possible severe intellectual deficiency and mild cognitive limitation were collected from healthcare records and registries for all children. Logistic regression estimated the odds of poor school performance or severe intellectual deficiency/mild cognitive limitation associated with exposure to maternal thyroid dysfunction. The odds of poor school performance associated with the adolescents' own thyroid function at age 16 were also estimated. Results are presented as odds ratios (OR) with confidence intervals (CI), adjusted for maternal/family covariates and child's sex.

RESULTS

Girls of mothers with subclinical hypothyroidism had more self-evaluated difficulties in mathematics than did girls of euthyroid mothers (OR 1.62 [CI 1.06-2.49]). Boys of hypothyroxinemic mothers repeated a school class more often than did boys of euthyroid mothers (OR 5.46 [CI 1.19-25.06]). Adolescents of hyperthyroid mothers had increased odds of poor self-evaluated performance in mathematics (OR 1.61 [CI 1.01-2.49]). Maternal thyroid dysfunction did not increase the odds of a child having severe intellectual deficiency/mild cognitive limitation. At 16 years of age, girls with hyperthyroidism by laboratory measurements had more difficulties in Finnish language (OR 2.82 [CI 1.42-5.61]) than did euthyroid girls. Boys with hypothyroxinemia by laboratory measurement had higher odds of having difficulties in Finnish and/or mathematics (OR 2.13 [CI 1.26-3.62]) than did euthyroid boys.

CONCLUSIONS

Maternal thyroid dysfunction during early pregnancy was associated with poorer scholastic performance of the adolescent. Additionally, adolescents' own thyroid dysfunction was associated with difficulties in school performance assessed by self-evaluation.

The impact of gestational thyroid hormone concentrations on ADHD symptoms of the child

CONTEXT

Maternal hypothyroidism during pregnancy is associated with adverse neuropsychological development in the offspring.

OBJECTIVE

The objective of the study was to evaluate the effect of maternal thyroid dysfunction during pregnancy on a child's attention-deficit/hyperactivity disorder (ADHD) symptoms.

DESIGN, SETTINGS, AND PARTICIPANTS

The prospective, population-based Northern Finland Birth Cohort 1986 (9362 pregnancies; 9479 infants) included analysis of maternal TSH, free T4, and thyroid-peroxidase antibodies (TPO-Abs) from early pregnancy samples (5791 women). Teachers evaluated the children's ADHD symptoms at 8 years using the Rutter B2 scale (5131 mother-child pairs), in which a high score indicated probable psychiatric disorders and three questions focused directly on ADHD.

MAIN OUTCOME MEASURES

The odds ratios (ORs) and 95% confidence intervals (95% CIs) of child having ADHD symptoms and/or a high Rutter B2 score after exposure to increases in maternal TSH levels (after logarithmic transformation), low free T4 levels, and TPO-Ab positivity was tested with logistic regression, adjusting for maternal/family covariates. Data were stratified by the child's gender due to interaction.

RESULTS

Among girls the odds of inattention (OR 1.18, 95% CI 1.02-1.37), high Rutter B2 total score (OR 1.23, 95% CI 1.03-1.48), and combined ADHD symptoms (OR 1.39, 95% CI 1.07-1.80) significantly increased with every natural log increase in maternal TSH concentrations. Such findings were not evident in boys. No associations were seen between ADHD symptoms and low maternal free T4 levels or TPO-Ab positivity.

CONCLUSIONS

Increases in maternal TSH in early pregnancy showed weak but significant association with girls' ADHD symptoms.

Elevated blood pressure in pregnancy and subsequent chronic disease risk

BACKGROUND

Preeclampsia, a new-onset hypertensive disorder of pregnancy, is associated with lifetime cardiovascular disease risk, but less is known about risk after other pregnancy-related hypertension.

METHODS AND RESULTS

The Northern Finland Birth Cohort 1966 included all expected births from 1 year (N=12 055 women). Blood pressure measurements and other prospective data were determined from prenatal care records and questionnaires for 10 314 women. Subsequent diagnoses were ascertained from Finnish registries (average follow-up, 39.4 years). Adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) estimate risks in hypertensive women compared with normotensive women. Hypertension during pregnancy was associated with increased risk of subsequent cardiovascular disease and arterial hypertension. Women with chronic hypertension and superimposed preeclampsia/eclampsia had high risk for future diseases. Gestational hypertension was associated with increased risk of ischemic heart disease (HR, 1.44 [95% CI, 1.24-1.68]), myocardial infarcts (HR, 1.75 [95% CI, 1.40-2.19]), myocardial infarct death (HR, 3.00 [95% CI, 1.98-4.55]), heart failure (HR, 1.78 [95% CI, 1.43-2.21]), ischemic stroke (HR, 1.59 [95% CI, 1.24-2.04]), kidney disease (HR, 1.91 [95% CI, 1.18-3.09]), and diabetes mellitus (HR, 1.52 [95% CI, 1.21-1.89]). Isolated systolic hypertension was associated with increased risk of myocardial infarct death (HR, 2.15 [95% CI, 1.35-3.41]), heart failure (HR, 1.43 [95% CI, 1.13-1.82]), and diabetes mellitus (HR, 1.42 [95% CI, 1.13-1.78]), whereas isolated diastolic hypertension was associated with increased risk of ischemic heart disease (HR, 1.26 [95% CI, 1.05-1.50]). Results were similar in nonsmoking women aged <35 years with normal weight and no diabetes mellitus during pregnancy.

CONCLUSIONS

Elevated blood pressure during pregnancy, regardless of type and even without known risk factors, signals high risk of later cardiovascular disease, chronic kidney disease, and diabetes mellitus. Clinical monitoring, risk factor evaluation, and early intervention could benefit women with hypertension in pregnancy.

Maternal thyroid dysfunction during pregnancy and thyroid function of her child in adolescence

CONTEXT

Normal maternal thyroid function is important for fetal development. No knowledge exists on how maternal thyroid function and thyroid antibodies during early pregnancy affect thyroid function of the offspring.

OBJECTIVE

The aim of this study was to investigate the relationship between maternal and adolescent thyroid function parameters.

DESIGN, SETTING, AND PARTICIPANTS

A total of 3673 mother-child pairs from the prospective, population-based Northern Finland Birth Cohort 1986 participated in the study. Maternal serum samples were drawn in early pregnancy (<20th gestational week), and children's samples were drawn at the age of 16 years and analyzed for TSH, free T4 (fT4), and thyroid peroxidase antibodies (TPO-Abs).

MAIN OUTCOME MEASURES

TSH, fT4, and TPO-Ab concentrations were measured at the age of 16 years. Children of mothers with thyroid dysfunction (hypothyroidism, hyperthyroidism, or hypothyroxinemia) or TPO-Ab positivity were compared to those of euthyroid or TPO-Ab-negative mothers. The distributions are expressed as medians with 5th to 95th percentiles.

RESULTS

Boys of hypothyroid mothers had higher TSH concentrations than those of euthyroid mothers: 2.0 (0.9-4.0) vs 1.7 (0.8-3.3) mU/L; P = .001. Children of hyperthyroid mothers had lower TSH concentrations than those of euthyroid mothers: 1.3 (0.6-4.2) vs 1.7 (0.8-3.3) mU/L, P = .013, for boys; and 1.3 (0.5-3.5) vs 1.6 (0.7-3.4) mU/L, P = .034, for girls. There were no differences in TSH or fT4 concentrations between children of hypothyroxinemic and euthyroid mothers. TPO-Ab-positive mothers more often had TPO-Ab-positive children (prevalence, 9.0 vs 3.7% among boys, and 22.7 vs 7.5% among girls).

CONCLUSIONS

Maternal thyroid dysfunction and TPO-Ab positivity during pregnancy seem to modify thyroid function parameters of offspring even in adolescence. Whether this increases the thyroid disease risk of the children is still unknown.

Preeclampsia, gestational hypertension and subsequent hypothyroidism

OBJECTIVES: To evaluate the effect of preeclampsia (PE) and gestational hypertension (GH) on subsequent hypothyroidism. Recent studies suggest that women with PE have increased risk for reduced thyroid function, but the association between PE and GH with overt hypothyroidism has not been examined. STUDY DESIGN: Two prospective population-based cohort studies, the Northern Finland Birth Cohorts 1966 and 1986, followed women who had PE (N=955), GH (N=1449) or were normotensive (N=13531) during pregnancy. Finnish national registers were used to confirm subsequent hypothyroidism. Adjusted hazard ratios (aHRs) with 95% confidence intervals (CIs) estimated hypothyroidism risk when comparing women with PE or GH with normotensive women. MAIN OUTCOME MEASURES: Primary hypothyroidism during follow-up of 20-40 years. RESULTS: The subsequent prevalence of hypothyroidism was higher among women with PE (4.0%) and GH (4.5%) compared with normotensive women (3.5%), but the risk increase was not significant (aHR for PE 1.13, 95%CI 0.80-1.59 and aHR for GH 1.11, 95%CI 0.85-1.45). Subgroup analysis among nulliparous women revealed a significant association between late PE and subsequent hypothyroidism (aHR 1.82, 95%CI 1.04-3.19). Early or recurrent PE were not associated with hypothyroidism (aHR 0.93, 95%CI 0.46-1.81 and aHR 1.35, 95%CI 0.63-2.88, respectively). CONCLUSIONS: Overall, PE or GH during pregnancy was not significantly associated with subsequent hypothyroidism in Finnish women after 20-40 years of follow-up. However, late PE in nulliparous women was associated with a 1.8-fold increased risk of subsequent hypothyroidism, a finding that merits further study in other populations.

Smoking and early pregnancy thyroid hormone and anti-thyroid antibody levels in euthyroid mothers of the Northern Finland Birth Cohort 1986

BACKGROUND

Smokers in the general population have lower thyrotropin (TSH) and higher free triiodothyronine (fT3) and free thyroxine (fT4) concentrations, but the results in pregnant population vary from no effect to a decrease in TSH and fT4 concentrations and an increase in fT3 levels. Our objective was to further evaluate the question of whether there is an association between smoking, before and during pregnancy, with maternal thyroid function during pregnancy and with the risk for subsequent hypothyroidism.

METHODS

Our study population was a prospective population-based cohort (N=9362), the Northern Finland Birth Cohort 1986, with extensive data throughout gestation. The mothers underwent serum sampling in early pregnancy. The samples were assayed for TSH, fT3, fT4, thyroid-peroxidase antibodies (TPO-Ab), and thyroglobulin antibodies (TG-Abs) (n=5805). Mothers with thyroid dysfunction diagnosed before or during pregnancy were excluded, leaving 4837 euthyroid mothers. The smoking status of mothers and fathers were requested by questionnaires during pregnancy. Subsequent maternal morbidity relating to hypothyroidism 20 years after the index pregnancy was evaluated using national registers.

RESULTS

Euthyroid mothers who smoked before, or continued smoking during first trimester of pregnancy, had higher serum fT3 (p<0.001) and lower fT4 (p=0.023) concentrations than nonsmokers. Smoking in the second trimester was associated with higher fT3 (p<0.001) concentrations, but no difference in fT4 concentrations compared with nonsmokers. TG-Abs were less common among smoking than nonsmoking mothers (2.5% vs. 4.7%, p<0.001), but the prevalence of TPO-Ab was similar. Paternal smoking had no independent effect on maternal early pregnancy thyroid hormone or antibody concentrations. The risk of subsequent maternal hypothyroidism after follow-up of 20 years was similar among prepregnancy smokers and nonsmokers.

CONCLUSIONS

In euthyroid women, smoking during pregnancy was associated with higher fT3 levels and lower fT4 levels; possibly reflecting smoking-induced changes in peripheral metabolism of thyroid hormones. No differences were found in TSH concentrations between smokers and nonsmokers. Our results differ from those of the general population, which usually have shown smoking-induced thyroidal stimulation. This is possibly due to pregnancy-induced changes in thyroid function. Decreases in fT4 levels among smokers might predispose to hypothyroidism or hypothyroxinemia during pregnancy. Despite these changes in thyroid function, smoking did not increase the woman's risk of subsequent hypothyroidism.

Early pregnancy reference intervals of thyroid hormone concentrations in a thyroid antibody-negative pregnant population

BACKGROUND

Thyroid dysfunction and antibodies are increasingly recognized as risk factors during pregnancy. Thyroid function changes during pregnancy and there is a need for gestational age-specific reference intervals for thyroid hormones. The aim of this study was to calculate gestational age-specific thyrotropin (TSH), free thyroxine (fT4), and free triiodothyronine (fT3) reference intervals in an iodine-sufficient thyroid antibody-negative population.

METHODS

The study population consisted of a large, prospective population-based cohort, the Northern Finland Birth Cohort 1986 (singleton births, n = 9362), with extensive data throughout gestation. The subjects underwent serum sampling in early pregnancy. Samples were assayed for TSH, fT4, fT3, thyroid-peroxidase, and thyroglobulin antibodies (n = 5805). All mothers with thyroid antibodies or previous thyroid diseases were excluded when calculating gestational age-specific percentile categories for TSH, fT4, and fT3. Also, associations between body mass index (BMI) and thyroid hormones were established.

RESULTS

The upper reference limit for TSH was 2.5 multiples of median (2.7-3.5 mU/L, depending on gestational week). The lower reference limit was as low as 0.07 mU/L. Reference intervals for fT4 rose during early pregnancy and decreased thereafter, ranging between 11-22 pmol/L. Reference intervals for fT3 were uniform throughout gestation, ranging between 3.4 and 7.0 pmol/L. BMI was associated positively with early pregnancy TSH and fT3 concentrations and negatively with fT4 concentrations.

CONCLUSIONS

These gestational age-specific reference intervals for thyroid hormones provide a framework for clinical decision making. Overweight and obesity are increasing problems among fertile women and they are associated with possibility of thyroid dysfunction during pregnancy.

Thyroid dysfunction and autoantibodies during pregnancy as predictive factors of pregnancy complications and maternal morbidity in later life

CONTEXT

Knowledge is scarce concerning the significance of thyroid dysfunction/antibodies during pregnancy in regard to pregnancy complications/later maternal morbidity.

OBJECTIVE

The aim of this study was to evaluate the association between maternal thyroid dysfunction/antibodies during pregnancy and pregnancy complications or later maternal hypertension, diabetes, and thyroid disease.

DESIGN AND SETTING

We studied a prospective population-based cohort, Northern Finland Birth Cohort 1986 (NFBC 1986), with follow-up of 20 yr. Medication and hospital discharge records were used to assess maternal morbidity to hypertension, diabetes, and thyroid diseases.

PARTICIPANTS

The study consisted of mothers of NFBC 1986 with early pregnancy serum samples for thyroid function and antibody analyses (n = 5805). Mothers were grouped and compared according to these test results.

MAIN OUTCOME MEASURES

We focused on preeclampsia and gestational diabetes during index pregnancy, later maternal hypertension, diabetes, and thyroid disease morbidity and total mortality.

RESULTS

Thyroid dysfunction and antibodies were not associated with pregnancy complications. Overt hypothyroidism was associated with subsequent maternal thyroid disease [hazard ratio (HR) (95% confidence interval), 17.7 (7.8-40.6)] and diabetes [6.0 (2.2-16.4)]. Subclinical hypothyroidism [3.3 (1.6-6.9)], TPO-Ab-positivity [4.2 (2.3-7.4)], and TG-Ab-positivity [3.3 (1.9-6.0)] were also associated with later thyroid disease. No association was found between thyroid dysfunction/antibodies and hypertension or overall mortality.

CONCLUSIONS

Thyroid dysfunction and antibodies during pregnancy seem to predict later thyroid disease. Overt hypothyroidism poses risk of diabetes.

Evaluation of innotrac aio! Second-generation cardiac troponin I assay: the main characteristics for routine clinical use

The availability of a simple, sensitive, and rapid test using whole blood to facilitate processing and to reduce the turnaround time could improve the management of patients presenting with chest pain. The aim of this study was an evaluation of the Innotrac Aio! second-generation cardiac troponin I (cTnI) assay. The Innotrac Aio! second-generation cTnI assay was compared with the Abbott AxSYM first-generation cTnI, Beckman Access AccuTnI, and Innotrac Aio! first-generation cTnI assays. We studied serum samples from 15 patients with positive rheumatoid factor but with no indication of myocardial infarction (MI). Additionally, the stability of the sample with different matrices and the influence of hemodialysis on the cTnI concentration were evaluated. Within-assay CVs were 3.2%-10.9%, and between-assay precision ranged from 4.0% to 17.2% for cTnI. The functional sensitivity (CV = 20 %) and the concentration giving CV of 10% were approximated to be 0.02 and 0.04, respectively. The assay was found to be linear within the tested range of 0.063-111.6 mu g/L. The correlations between the second-generation Innotrac Aio!, Access, and AxSYM cTnI assays were good (r coefficients 0.947-0.966), but involved differences in the measured concentrations, and the biases were highest with cTnI at low concentrations. The second-generation Innotrac Aio! cTnI assay was found to be superior to the first-generation assay with regard to precision in the low concentration range. The stability of the cTnI level was best in the serum, lithium-heparin plasma, and lithium-heparin whole blood samples (n = 10 , decrease < 10 % in 24 hours at +20( degrees )C and at +4( degrees )C. There was no remarkable influence of hemodialysis on the cTnI release. False-positive cTnI values occurred in the presence of very high rheumatoid factor values, that is, over 3000 U/L. The 99th percentile of the apparently healthy reference group was </= 0.03 mu g/L. The results demonstrate the very good analytical performance of the second-generation Innotrac Aio! cTnI assay.

Lipid peroxides, glutathione peroxidase, high density lipoprotein subfractions and apolipoproteins in young adults

Lipid peroxides have been implicated in the initiation of atherogenesis. In this study of 23 young healthy subjects, high levels of serum lipid peroxides were associated with low serum HDL2 cholesterol concentrations and low HDL2/HDL3 cholesterol and apolipoprotein A-I/A-II ratios. Low levels of LDL cholesterol and apolipoprotein B, and low apolipoprotein B/A-I ratios were typical of subjects with high serum glutathione peroxidase activities. Serum lipid peroxide levels varied widely in subjects without abnormal cholesterol, HDL cholesterol or LDL cholesterol concentrations. This variation may play a role in the frequent occurrence of coronary artery disease in normolipidaemic individuals.

Time-resolved fluoroimmunoassay of 5-methyl-2'-deoxycytidine employing europium-labeled antigen as tracer

We describe a solid-phase fluoroimmunoassay, based on competition between europium-labeled 5 MeCyd (5-methylcytidine) and sample 5MedCyd (5-methyl-2'-deoxycytidine) for polyclonal anti-5MedCyd antibodies (rabbit). Europium labeling of antigen was performed using a novel polylysine-5MeCyd conjugate. Standard and sample preparations containing 5MedCyd inhibited the binding of the europium-labeled 5MeCyd to the antibody molecules. A second antibody, directed against rabbit IgG, was coated on the solid phase, and bound the IgG-5MeCyd-polylysine-europium complex, giving rapid and complete separation of antibody-bound and free antigen. The measuring range was from 3.7 to 2500 pmol of 5MedCyd per assay. A good correlation between the results obtained with TR-FIA and HPLC was demonstrated when the methods were applied to the measurement of methylation in various DNA samples, enzymatically hydrolyzed to their constituent deoxyribonucleosides. This new TR-FIA possesses the same advantages (high sensitivity, wide assay range, rapidity, simplicity, and low cost) as the previous assay developed in our laboratories. The superiority of the new system is based on (i) its low inter- and intra-assay variation, (ii) low antiserum consumption, and (iii) a protocol, which permits the use of second-antibody-coated microtitration strips common to other assays.

Radioimmunoassay of 5-hydroxymethyl-2'-deoxyuridine

5-Hydroxymethyl-2'-deoxyuridine is an antileukemic thymidine analogue. It is also a well known thymidine-derivative in DNA exposed to ionizing irradiation. We report the production and characterization of specific rabbit anti-5HmdUrd antisera. The antisera were used for the radioimmunological measurement of 5HmdUrd. The radioimmunoassay was capable of quantitating 2 pmol of 5 HmdUrd per tube corresponding to 0.2 mumol/l in a 10 microliter plasma sample. A good correlation between the results obtained with the radioimmunoassay and HPLC was demonstrated when the methods were applied to the measurement of plasma levels of 5HmdUrd in mice receiving experimental chemotherapy.

Antileukemic activity against L1210 leukemia, pharmacokinetics and hematological side effects of 5-hydroxymethyl-2'-deoxyuridine

The chemotherapeutic potential of 5-hydroxymethyl-2'-deoxyuridine (5HmdUrd) was examined in vitro and in vivo. The compound was toxic in 2-day cultures; 7, 66 and 88% inhibition in the growth of L1210 cells was achieved with 1, 10 and 100 microM 5HmdUrd, respectively. The maximal plasma concentration of 5HmdUrd at 15 min after a single i.p. injection (100 mg/kg) in DBA/2 mice was 193-244 mumol./l and the compound had a logarithmic disappearance curve with a half-life of 20 min. Chemotherapy given as two daily i.p. injections of 5HmdUrd (100 mg/kg) for five successive days resulted in a 239% increase in median lifespan and 2/6 long-term survivals among DBA/2 mice bearing leukemia L1210. This treatment resulted in temporary neutropenia and thrombocytopenia, which were followed by rebound thrombocytosis and neutrophilia of short duration. Our data indicate that 5HmdUrd can successfully be used in experimental cancer chemotherapy in vivo.

Time-resolved fluoroimmunoassay of 5-methyl-2'-deoxycytidine

We describe time-resolved fluoroimmunoassay of 5-methyl-2'-deoxycytidine (5MedCyd). The assay is based on the use of a highly specific antiserum raised in rabbits against BSA-conjugated 5-methylcytidine (5MeCyd). The tracer in the solid-phase time-resolved fluoroimmunoassay (TR-FIA) was antigen-selected anti-5MedCyd labeled with Europium. Thyroglobulin-linked 5MeCyd served as the solid-phase antigen. The measuring range for the fluoroimmunoassay was from less than 1 to 5000 pmol per assay of 5MedCyd. A good correlation between the results obtained with the TR-FIA and HPLC was demonstrated when the methods were applied to the measurement of methylation in human leukemic cells and other DNA samples. TR-FIA has several advantages over the more laborious techniques available so far: (i) high sensitivity, (ii) large assay ranges, (iii) rapidity and large number of simultaneous assays, (iv) simplicity, and (v) low cost provided that the laboratory has equipment for time-resolved fluorometry.

An improved radioimmunoassay for the quantitation of DNA methylation

A novel radioimmunoassay of 5MedCyd is described. The assay, employing a highly specific antiserum raised in rabbits against BSA-conjugated 5MeCyd, used 5-125iodo-2'-deoxycytidine as the tracer. The measuring range for the assay was found to be 1-1000 pmol per assay of 5MedCyd. When the methods were applied to the measurement of methylation in DNA samples a good correlation between the results obtained with the radioimmunoassay and HPLC was demonstrated. The method has several advantages over the more laborious and sophisticated techniques previously available: high sensitivity, large assay range, rapidity and potential for large number of simultaneous assays, simplicity, and low cost provided that the laboratory has equipment for gamma counting.