Abstract
Thyroid dysfunction is frequent in pregnant women and is often associated with an increased risk of adverse maternal and fetal outcome. In the present work, thyroid function of pregnant women from Benin republic was studied. Two hundred forty (240) pregnant women, without thyroid disease history, have been included in the study. A blood sample was drawn for measurement of TSH, free T3 and free T4 serum levels. From the first to the third trimester, plasma levels of free T3 and free T4 decreased when plasma levels of TSH increased. Using recommendations of the 2011 American Thyroid Association (ATA) guidelines, thyroid dysfunction was observed in 24.17% of subjects. Hypothyroidism was present in 22.50% of subjects with 19.17% of subclinical hypothyroidism, 0.83% of overt hypothyroidism and 2.50% of hypothyroxinemia and hyperthyroidism was observed in 1.67% of subjects. An increase from 15.52% to 28.07% was observed in the frequency of hypothyroidism from the first to the third trimester of pregnancy. When an upper cut-off value of 4 mU/L was used for TSH, as recommended in the 2017 ATA guidelines, prevalence of thyroid disorders was 14.58% with 12.91% of hypothyroidism but no hypothyroidism was observed in women in the first trimester of pregnancy. A rise in hypothyroidism frequency was observed when pregnant women age increased. Hypothyroidism was very common in pregnant women in Benin. To allow accurate assessment of thyroid status in pregnant women in Benin, pregnancy specific range for plasma level of TSH and thyroid hormones should be established.
Highlights
Pregnancy is a physiological state in which significant changes in thyroid function occur
Using recommendations of the 2011 American Thyroid Association (ATA) guidelines, thyroid dysfunction was observed in 24.17% of subjects
An increase from 15.52% to 28.07% was observed in the frequency of hypothyroidism from the first to the third trimester of pregnancy
Summary
Pregnancy is a physiological state in which significant changes in thyroid function occur. Since the beginning of pregnancy, the hCG (human chorionic gonadotrophin) secreted by the placenta, given its homology of structure with TSH (thyroid stimulating hormone), exerts a stimulatory effect on thyroid gland leading to an increase in the secretion of thyroid hormones (T3 and T4) and a decrease in TSH, especially during the first trimester. Demand for iodine intake increases especially as there is a greater urinary excretion of iodine and a transfer of iodine to the fetus when his thyroid becomes functional [1] [2]. All these factors could contribute to thyroid dysfunction during pregnancy especially when a deficiency of iodine intake exists and when thyroid reserve is not sufficient
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