Prevalence of thyroid deficiency in pregnant women

Department of Maternal and Child Health, Dartmouth Medical School, Hanover, NH 03756.
Clinical Endocrinology (Impact Factor: 3.35). 08/1991; 35(1):41-6. DOI: 10.1111/j.1365-2265.1991.tb03494.x
Source: PubMed

ABSTRACT The present study was designed to determine the current prevalence of gestational hypothyroidism, since maternal thyroxine deficiency is associated with poor obstetric outcomes and mental retardation in the surviving offspring.
TSH concentrations were measured in the sera of women at 15-18 weeks of gestation. Those sera with TSH concentrations above 6 mU/l and the two sera closest in order with TSH concentrations below 6 mU/l were further analysed for T4, FT4, TBG, and antithyroid antibodies. Study criteria for hypothyroidism were sera with elevated concentrations of TSH plus both a free T4 concentration and a total T4 concentration and/or T4/TBG ratio more than two standard deviations below the mean for the control pregnant women.
The sera were from 2000 consecutive women in Maine being tested for alpha-fetoprotein concentration at 15-18 weeks of gestation.
TSH concentrations above 6 mU/l were found in the sera of 49 women, 2.5% of the pregnant women. Six women with elevated TSH concentrations (range 6.9-54 mU/l) had both a FT4 concentration and a T4/TBG ratio and/or a T4 concentration more than two standard deviations below the respective control means, meeting the study criteria for thyroid deficiency, and thus giving a prevalence of 0.3%. The remaining 43 women with elevated TSH concentrations were classified as having compensated thyroid disease although some may have been hypothyroid. Fifty-eight per cent of women with TSH concentrations above 6 mU/l and 90% of the women with elevated TSH concentrations and at least one thyroxine index more than two standard deviations below the control means had positive titres of antithyroid antibodies as opposed to 11% of the controls.
Although it is not known what severity of maternal thyroid deficiency is necessary to cause fetal brain damage, the present data indicate a sufficiently high prevalence of thyroid dysfunction to demand investigation of the mental development of the offspring of women with thyroid dysfunction and of the effect of replacement therapy.

  • Source
    • "Thyroid disorders are commonly present in pregnancy and puerperium. Hypothyroidism has a higher prevalence than hyperthyroidism (2.5 versus 0.2%) during the gestational period [3]. Early and appropriate detection of thyroid dysfunction and timely interventions improve maternal-fetal prognosis, so application of reliable gestational specific reference values for determining thyroid disorders in pregnant women would be a necessity [4]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background. Due to many physiological changes during pregnancy, interpretation of thyroid function tests needs trimester-specific reference intervals for a specific population. There is no normative data documented for thyroid hormones on healthy pregnant women in Iran. The present survey was conducted to determine trimester-specific reference ranges for serum TSH, thyroxine (TT4), and triiodothyronine (TT3). Methods. The serum of 215 cases was analyzed for measurement of thyroid function tests by immunoassay method of which 152 iodine-sufficient pregnant women without thyroid autoantibodies and history of thyroid disorder or goiter were selected for final analysis. Reference intervals were defined as 5th and 95th percentiles. Results. Reference intervals in the first, second, and third trimesters were as follows: TSH (0.2-3.9, 0.5-4.1, and 0.6-4.1 mIU/l), TT4 (8.2-18.5, 10.1-20.6, and 9-19.4 μg/dl), and TT3 (137.8-278.3, 154.8-327.6, and 137-323.6 ng/dl), respectively. No correlation was found between TSH and TT4 or TT3. Significant correlation was found between TT4 and TT3 in all trimesters (r = 0.35, P < 0.001). Conclusion. The reference intervals of thyroid function tests in pregnant women differ among trimesters. Applying trimester-specific reference ranges of thyroid hormones is warranted in order to avoid misclassification of thyroid dysfunction during pregnancy.
    06/2013; 2013:651517. DOI:10.1155/2013/651517
  • Source
    • "Later in pregnancy and during lactation, maternal thyroid hormones still contribute significantly to foetal thyroid homeostasis [6– 8]. Worldwide, both overt and subclinical hypothyroidism are frequent among fertile women [9] [10] [11] [12] [13] [14]. Prior maternal thyroid diseases as well as iodine and selenium deficiencies are known risk factors for hypothyroidism. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Maternal euthyroidism during pregnancy is crucial for normal development and, in particular, neurodevelopment of the foetus. Up to 3.5 percent of pregnant women suffer from hypothyroidism. Industrial use of various chemicals—endocrine disrupting chemicals (EDCs)—has been shown to cause almost constant exposure of humans with possible harmful influence on health and hormone regulation. EDCs may affect thyroid hormone homeostasis by different mechanisms, and though the effect of each chemical seems scarce, the added effects may cause inappropriate consequences on, for example, foetal neurodevelopment. This paper focuses on thyroid hormone influence on foetal development in relation to the chemicals suspected of thyroid disrupting properties with possible interactions with maternal thyroid homeostasis. Knowledge of the effects is expected to impact the general debate on the use of these chemicals. However, more studies are needed to elucidate the issue, since human studies are scarce.
    09/2011; 2011:342189. DOI:10.4061/2011/342189
  • Source
    • "The prevalence of hypothyroidism during pregnancy is estimated to be 0.3–0.5% for overt hypothyroidism (OH) and 2-3% for subclinical hypothyroidism (SH). Thyroid autoantibodies are found in 5–18% of women in the childbearing age, and chronic autoimmune thyroiditis (AITD) is the main cause of hypothyroidism during pregnancy in iodide sufficient areas [7] [8] [9]. However, on a worldwide basis the most important cause of thyroid insufficiency remains iodine deficiency [10]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The prevalence of overt and subclinical hypothyroidism during pregnancy is estimated to be 0.3-0.5% and 2-3%, respectively. Thyroid autoantibodies are found in 5-18% of women in the childbearing age. The aim of this review is to underscore the clinical significance of these findings on the health of both the mother and her offspring. Methods of evaluation of thyroid function tests (TFTs) during pregnancy are described as are the threshold values for the diagnosis of overt and subclinical hypothyroidism or hypothyroxinemia. Anticipated differences in TFTs in iodine-sufficient and iodine-deficient areas are discussed and data are provided on potential complications of hypothyroidism/hypothyroxinemia and autoimmune thyroid disease during pregnancy and adverse effects for the offspring. The beneficial effects of levothyroxine therapy on pregnancy outcomes and offspring development are discussed with a proposed treatment regimen and follow up strategy.
    08/2011; 2011:843591. DOI:10.4061/2011/843591
Show more