Özet:

The aim of this study is to examine the frequency of thyroid dysfunction in the first trimester based on two different reference ranges, and to compare the results. To determine the exact prevalence of thyroid dysfunction among pregnant women in Turkey. We retrospectively reviewed and recorded first trimester TSH, fT4 and fT3 levels of patients, who were presented to the gynecology and obstetrics outpatient clinics of our hospital, which is a tertiary healthcare center. Totally 647 patients were included in the study. The frequency of thyroid dysfunction was evaluated based on two different reference ranges for TSH levels as 0.1-2.5 mIU/L and 0.34-5.6 mIU/L. Based on a TSH reference range of 0.1–2.5 mIU/L, 525 (81.14%) patients were euthyroid, 16 (2.47%) had hyperthyroidism, and 106 (16.38%) had hypothyroidism. Based on a TSH reference range of 0.34-5.6 mIU/L, 582 (89.95%) patients were euthyroid, 50 (7.72%) had hyperthyroidism, and 15 (2.31%) had hypothyroidism. The two different reference ranges yielded significantly different prevalences of thyroid dysfunction and hence, would lead to a significant difference in terms of clinical approach to patients. When we used the current recommended reference range for TSH, we detected a remarkably higher prevalence of thyroid dysfunction among pregnant women in our region in comparison to the literature. This condition may be explained with endemic iodine deficiency. However, in our opinion, it would be best to revise the recommended reference range for TSH for our country via long-term follow-up studies that compare perinatal outcomes with pregnancy TSH levels.

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