Thyroid function in pregnancy

Abstract

Advances in understanding the physiology of thyroid function in normal pregnancy have highlighted the importance of the consequences of abnormal function on obstetric outcome and foetal well-being. Pubmed search was done using the terms thyroid and pregnancy. Areas of agreement are the following: gestational normative reference ranges for thyroid function tests are required for proper interpretation of any abnormalities. Measurement of thyroid-stimulating antibodies and antithyroid peroxidase antibodies is useful for diagnosis of thyroid disease in pregnancy. Treatment of Graves’ hyperthyroidism should be done with propylthiouracil for first trimester only, then carbimazole or methimazole. Patients on levothyroxine require an increase in dosage during gestation. Areas of controversy are the following: total thyroxine (TT4) versus Free T4 (FT4) assays in pregnancy. Screening for thyroid function in early gestation: should it be routinely performed on everyone? What tests are appropriate? Growing points are the following: physiology of thyroxine delivery to the foetus. Establishment of gestational thyroid hormone reference ranges. Evaluation of strategies to screen thyroid function in early pregnancy. Areas timely for developing research are the following: placental thyroid hormone physiology, thyroid hormone therapy and screening thyroid function.