Prevalence of thyroid deficiency in pregnant women

Department of Maternal and Child Health, Dartmouth Medical School, Hanover, NH 03756.
Clinical Endocrinology (Impact Factor: 3.46). 08/1991; 35(1):41-6. DOI: 10.1111/j.1365-2265.1991.tb03494.x
Source: PubMed


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.

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    • "offspring (Glinoer, 1997; Glinoer and Delange, 2000; Haddow et al., 1999; Klein et al., 1991; Pop et al., 1999). Results from the literatures show that the PCP concentrations in maternal and/or cord blood samples are generally below 10 ng/g (Dallaire et al., 2009; Guvenius et al., 2003; Meijer et al., 2008; Meijer et al., 2012; Park et al., 2008; Roze et al., 2009), and PCA are generally below 1 ng/g (Damgaard et al., 2006; Shen et al., 2007). "
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    ABSTRACT: Pentachloroanisole (PCA) and pentachlorophenol (PCP) are chlorinated aromatic compounds that have been found in the environment and in human populations. The objective of this study is to characterize the effects of PCA in comparison to those of PCP on development at environmental relevant levels using a fish model. Zebrafish embryos were exposed to 0.1, 1, 10, 100, 500, 1000 μg/L PCA and PCP respectively for 96 h. Malformation observation, LC50 testing for survival rate at 96 hours post fertilization (hpf) and EC50 testing for hatching rate at 72 hpf indicated that the developmental toxicity of PCP was about 15 times higher than that of PCA. PCP exposure at 10 μg/L resulted in elevated 3, 3′, 5-triiodothyronine (T3) levels and decreased thyroxine (T4) levels, whereas PCA had no effects on T3 or T4 levels. PCP and PCA exposure at 1 and 10 μg/L showed possible hyperthyroid effects similar to that of T3, due to increased relative mRNA expression of synapsin I (SYN), iodothyronine deiodinase type III (Dio3), thyroid hormone receptor alpha a (THRαa) and thyroid hormone receptor beta (THRβ), and decreased expression of iodothyronine deiodinase type II (Dio2). The results indicate that both PCA and PCP exposure can cause morphological deformities, possibly affect the timing and coordination of development in the central nervous system, and alter thyroid hormone levels by disrupting thyroid hormone regulating pathways. However, the developmental toxicity of PCA is at least ten times lower than that of PCP. Our results on the relative developmental toxicities of PCA and PCP and the possible underlying mechanisms will be useful to support interpretation of envrionmental concentrations and body burden levels observed in human populations.
    Full-text · Article · Feb 2015 · Ecotoxicology and Environmental Safety
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    • "Incidences of overt hyperthyroidy and overt hypothyroidy were determined to be 0.2% (2/891) and 0.2% (2/891), respectively. In the literature, general hyperthyroidy frequency in all of the pregnancies was shown to be 0.1-0.4% and hypothyroidy frequency in the pregnant women screened to be 0.3-0.5%.5,13-16 When the entire study group was evaluated, the incidence of hyperthyroidy and hypothyroidy during pregnancy in our hospital were 2.8% (28/998) and 4.3% (43/998), respectively. "
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    ABSTRACT: Objective: Primary objective of our study was to evaluate the efficiency of detailed medical history and thyroid examination of the pregnant women presenting to our clinic from Rize province and nearby which was an endemic goiter region. It was aimed to investigate the frequency of thyroid diseases, pregnancy outcomes and the efficiency of screening with thyroid function tests during the first trimester of pregnancy as secondary endpoint. Methodology : A prospective clinical study was conducted with 998 pregnant women between the ages of 17-48 years. In the first step of our study, a detailed medical history was obtained and a detailed thyroid gland examination was performed in all the patients (n=998). In the patients diagnosed with thyroid disease or considered to have thyroid disease with these results (n=107), thyroid diseases were evaluated with thyroid function tests and imagining methods. Analyses of socio-demographic data and nutrition were also made. In the second step, thyroid stimulating hormone (TSH), free T3 and free T4 tests were performed in the first antenatal examination of the pregnant cases considered not to have thyroid disease after medical history and examination (n=891). Parameters of thyroid peroxidase antibodies (TPOAb), thyroglobulin antibodies (TgAb) and TSH receptor auto antibodies (TRAb) were investigated in the cases whose TSH, sT3 and sT4 levels were different than the reference values after examination of the endocrinologist. Thyroid ultrasonography was performed. Urinary iodine levels in 24 hour urine were investigated. Results: During pregnancy, the incidence of hyperthyroidism and hypothyroidism in the whole study group were 2.8% (28/998) and 4.3% (43/998), respectively, 6.7% of the patients (67/998) had a diagnosis of thyroid disease before pregnancy. Hyperthyroidism and hypothyroidism depending on the TSH screening results were 1.9% (17/891) and 1.1% (10/891) respectively and the incidence of overt hyperthyroidism and overt hypothyroidism were 0.2% (2/891) and 0.2% (2/891) in the pregnant cases considered not to have thyroid disease with medical history and examination. Conclusion: Detailed medical history and family history obtained during the first trimester of pregnancy helped us to identify 6.7% of thyroid diseases among the pregnant women. This result effectively emphasizes the importance of detailed first prenatal examination regarding the thyroid.
    Full-text · Article · Sep 2013 · Pakistan Journal of Medical Sciences Online
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    • "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]. "
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    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.
    Full-text · Article · Jun 2013 · Journal of Thyroid Research
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