Dataset Information

Thyroid function parameters in normal pregnancies in an iodine sufficient population.

ABSTRACT:

Background

The aim of this retrospective observational study was to describe thyroid function parameters (fT3, fT4 and TSH) in the course of normal pregnancies.

Methods

Data were obtained between 2006 and 2007 at the University Hospital in Innsbruck, Austria. The starting point was the identification of women who had had a normal birth as recorded in the birth registry of Tyrol. Thyroid function parameters were determined using methods implemented at the Department of Nuclear Medicine in Innsbruck.

Results

The fT3 and fT4 values were normally distributed. Grouping the results by trimester revealed the following values: 4.93 ± 0.59, 4.54 ± 0.48, and 4.27 ± 0.45 pmol/l for fT3; and 15.23 ± 2.43, 13.79 ± 1.99, and 13.32 ± 0.2.01 pmol/l for fT4, respectively. The values corresponding to the 10th-percentile were 3.9 pmol/l for fT3 and 11.3 pmol/l for fT4, respectively. TSH values showed a typical left skewed distribution, thus the mean values were calculated after log transformation of the data. The corresponding mean trimestral values for TSH were 1.46 ± 1.29, 1.68 ± 1.23, and 1.70 ± 2.22 mIU/l, respectively.

Conclusion

In an iodine sufficient population, thyroid function parameters in normal pregnancies do not differ from those in non-pregnant women. Our previously defined reference range for TSH of 0.3 to 3.5 mIU/l is equally valid for normal pregnancies.

General significance

The question of cognition and IQ development of children has been proposed to be associated with thyroid function. The addition of data regarding normal thyroid function during pregnancy will contribute to this research.

SUBMITTER: Moncayo R

PROVIDER: S-EPMC4661549 | biostudies-literature | 2015 Jun

REPOSITORIES: biostudies-literature

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Publications

Thyroid function parameters in normal pregnancies in an iodine sufficient population.

Moncayo Roy R Zanon Birgit B Heim Kurt K Ortner Karina K Moncayo Helga H

BBA clinical 20150102

<h4>Background</h4>The aim of this retrospective observational study was to describe thyroid function parameters (fT3, fT4 and TSH) in the course of normal pregnancies.<h4>Methods</h4>Data were obtained between 2006 and 2007 at the University Hospital in Innsbruck, Austria. The starting point was the identification of women who had had a normal birth as recorded in the birth registry of Tyrol. Thyroid function parameters were determined using methods implemented at the Department of Nuclear Medi ...[more]

PMID: 26674060

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Project description:BACKGROUND:Studies indicate that mild to moderate iodine deficiency in pregnancy may have a long-term negative impact on child neurodevelopment. These effects are likely mediated via changes in maternal thyroid function, since iodine is essential for the production of thyroid hormones. However, the impact of iodine availability on thyroid function during pregnancy and on thyroid function reference ranges are understudied. The aim of this study was to investigate the association between iodine intake and thyroid function during pregnancy. DESIGN:In a population-based pregnancy cohort including 2910 pregnant women participating in The Norwegian Mother and Child Cohort Study, we explored cross sectional associations of maternal iodine intake measured (1) by a food frequency questionnaire and (2) as iodine concentration in a spot urine sample, with plasma thyroid hormones and antibodies. RESULTS:Biological samples were collected in mean gestational week 18.5 (standard deviation 1.3) and diet was assessed in gestational week 22. Median iodine intake from food was 121??g/day (interquartile range 90, 160), and 40% reported use of iodine-containing supplements in pregnancy. Median urinary iodine concentration (UIC) was 59??g/L among those who did not use supplements and 98??g/L in the women reporting current use at the time of sampling, indicating mild to moderate iodine deficiency in both groups. Iodine intake as measured by the food frequency questionnaire was not associated with the outcome measures, while UIC was inversely associated with FT3 (p?=?0.002) and FT4 (p?<?0.001). Introduction of an iodine-containing supplement after gestational week 12 was associated with indications of lower thyroid hormone production (lower FT4, p?=?0.027, and nonsignificantly lower FT3, p?=?0.17). The 2.5th and 97.5th percentiles of TSH, FT4, and FT3 were not significantly different by groups defined by calculated iodine intake or by UIC. CONCLUSION:The results indicate that mild to moderate iodine deficiency affect thyroid function in pregnancy. However, the differences were small, suggesting that normal reference ranges can be determined based on data also from mildly iodine deficient populations, but this needs to be further studied. Introducing an iodine-containing supplement might temporarily inhibit thyroid hormone production and/or release.

Project description:Background: There are scarce data on the prevalence of thyroid disorders and urinary iodine status among tribal populations of India, with no reported data from Kashmir valley. Objectives: To estimate the prevalence of thyroid disorders and evaluate urinary iodine concentration (UIC) and thyroid autoantibody status among Gujjar and Bakerwal tribes of Kashmir valley. Methods: This cross-sectional study recruited tribal subjects using multistage cluster sampling from 5 out of 22 districts of Jammu and Kashmir (J&K). Using a predesigned questionnaire, the details of past or current medical history and drug intake, including thyroid hormone medication etc. were recorded after obtaining an informed consent. Examination included anthropometry (height, weight, waist circumference), blood pressure measurement, and relevant general physical examination focusing on goiter palpation, while as laboratory assessment included estimation of serum thyroid hormone levels, antithyroid peroxidase antibody (anti-TPO Ab), and urinary iodine concentration. Results: A total of 763 subjects (56.4% women and 43.6% men) with a mean(±SD) age of 39.46 (±17.51) ranging from 10 to 85 years and mean(±SD) body mass index (BMI) of 21.28 (±4.16) kg/m2 were studied. Goiter was detected in 6.8%, while 33.2% subjects had some form of thyroid dysfunction (including 24.1% subclinical and 6.8% overt hypothyroidism). Subclinical and overt hyperthyroidism were observed in 1.3 and 0.9% of cases, respectively. Anti-TPO Ab was elevated in 13.6%, while the median [interquartile range (IQR)] for UIC was 154.50 (135) μg/L [156.13 (134) μg/L in men and 147.26 (136) μg/L in women]. A negative correlation was observed between UIC and anti-TPO Ab (r = -0.087, P = <0.05). Conclusion: These novel data on iodine and thyroid status among a tribal population of India generally inhabiting in remote sub-Himalayan belts demonstrate high prevalence of subclinical hypothyroidism (SCH) with persistent iodine deficiency. These preliminary data may warrant large well-designed studies to carry out comprehensive assessment of the problem in this high-risk and marginalized population.

Project description:BackgroundWhereas the adverse effects of severe iodine deficiency during pregnancy are well documented, the effects of mild-to-moderate deficiency are not well established.ObjectivesWe aimed to explore whether iodine nutrition and timing of iodine supplement initiation are associated with thyroid function in pregnant and postpartum women.MethodsIn this cohort study, 137 pregnant women were enrolled and followed up at gestational weeks (GWs) 18 and 36, and 3 and 6 mo postpartum. Thyroid function tests [thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), and free thyroxine (fT4)], urinary iodine and creatinine concentration (UIC:Cr), and iodine intake (including iodine supplement use) were measured at each time point. The associations between thyroid hormone concentrations and UIC:Cr, iodine intakes, and iodine supplement use were estimated using multiple generalized estimating equation models.ResultsThe median UIC at GW18 was 94 μg/L, indicating mild-to-moderate iodine deficiency. UIC:Cr (β; 95% CI) per 100 μg/g was negatively associated with fT3 (-0.191; -0.331, -0.051) and fT4 (-0.756; -1.372, -0.141) concentrations. Iodine intake (β; 95% CI) per 100 μg/d was positively associated with TSH (0.099; 0.022, 0.177), and negatively associated with fT3 (-0.084; -0.0141, -0.027) and fT4 (-0.390; -0.599, -0.182) concentrations. Compared with no use of supplement, those initiating an iodine-containing supplement prepregnancy and continuing through pregnancy had lower TSH (estimated means) (1.35 compared with 1.68 mIU/L, P = 0.021), and higher fT3 (4.48 compared with 4.28 pmol/L, P = 0.035) and fT4 (15.2 compared with 14.4 pmol/L, P = 0.024) concentrations.ConclusionsLower iodine availability during pregnancy and postpartum was associated with lower TSH, and higher fT3 and fT4 concentrations. The use of an iodine-containing supplement that was initiated prepregnancy and continuing through pregnancy was associated with lower TSH, and higher fT3 and fT4 concentrations, which may suggest improved thyroid function. These findings support the notion that optimization of iodine intake should start before pregnancy.This trial was registered at clinicaltrials.gov as NCT02610959.

Dataset Information

Thyroid function parameters in normal pregnancies in an iodine sufficient population.

Background

Methods

Results

Conclusion

General significance

Publications

Thyroid function parameters in normal pregnancies in an iodine sufficient population.

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