The incidence of thyroid dysfunction in pregnant women

Objective: Despite the different data presented in the literature, there is no satisfactory data for the incidence of thyroid dysfunction during pregnancy in Turkey where iodine deficiency is prevalent. In this study, we aimed to present the incidence of thyroid dysfunction during pregnancy. Methods: A total of 1876 pregnant women, whose thyroid stimulating hormone (TSH) and free T4 values were checked, were included in the study. Weeks of gestations, TSH and free T4 serum levels according to the last menstrual date and ultrasonography were retrospectively screened from the archive of our hospital. TSH reference ranges were accepted as 0.1–2.5 mU/l in the first trimester, 0.2–3.0 mU/l in the second trimester and 0.3–3.0 mU/l in the third trimester. The patients with high TSH value special to the trimester and low free T4 value were considered to have overt hypothyroidism, those with low TSH value and high free T4 value were considered to have overt hyperthyroidism, and the cases with abnormal TSH value but normal free T4 value were considered to have subclinical thyroid dysfunction. Results: Mean age of the pregnant women included in the study was found as 29.14±5.84 years. While 65.4% (n=1227) of the cases were in their first trimester, 21.1% (n=395) of them were in the second trimester, and 13.5% (n=254) of them were in the third trimester. Hyperthyroidism was found in 5.38% (n=101) of the pregnant women; while 1.22% (n=23) of them had overt hyperthyroidism, 4.16% (n=78) of them had subclinical hyperthyroidism. Of the cases, 15.88% (n=298) had hypothyroidism where 10.18% (n=191) of them had overt hypothyroidism and 5.70% (n=107) of them had subclinical hypothyroidism. Conclusion: In the pregnant women included in the study, we observed a high rate of hypothyroidism since TSH upper limit was possibly decreased in the first trimester and we were in a risky region for iodine deficiency.