Evaluation of maternal thyroid autoimmune status in gestational trophoblastic disorders

Hyperthyroidism or increased thyroid function has been reported in many patients with trophoblastic tumors, either hydatidiform mole or choriocarcinoma (1). In the US, hydatidiform mole occurs between 0.5 and 2.5 per 1000 pregnancies (2). It is more common in Asian and Latin American countries (3). Hydatidiform moles secrete large amounts of human chorionic gonadotropin (hCG), and the hCG level is proportional to the mass of the tumor (3). The prevalence of increased thyroid function in patients with hydatidiform mole has been reported as 25-64%. About 5% have clinical hyperthyroidism (4). On the other hand, around 0.3-0.5% of all pregnant women will have overt hypothyroidism (OH) that is associated with an increased risk for adverse pregnancy complications such as premature delivery, low birth weight, miscarriage, as well as detrimental effects on fetal neurocognitive development when untreated. Thyroid autoimmunity and subclinical hypothyroidism are more common than OH, affecting 11% and 2-2.5% of reproductive aged women, respectively (5). Thyroid peroxidase (TPO) is a key enzyme in the production of thyroid hormones, and a major autoantigen in autoimmune thyroid diseases (6). Thyroglobulin (Tg) (also called thyroid antibody 1) is a dimeric protein produced by the follicular cells of the thyroid (7). Both TPO and Tg are essential in the synthesis and secretion of thyroid hormones, including thyroxine (T4) and triiodothyronine (T3) (7). Autoantibodies to TPO (anti-TPO) and Tg (anti-Tg) are considered secondary responses and indicative of thyroid inflammation, and can be detected in 10-20% of women at childbearing age (8). Production of the above autoantibodies implicates the activation of an autoimmune process in the thyroid gland, but the majority of women with positive thyroid autoantibodies are euthyroid, that is, they have normal thyroid function. The association between gestational trophoblastic diseases and maternal thyroid functions was well established in previous studies. However, there was a lack of information about the relation between thyroid autoimmunity and molar pregnancies. In the present study, we aimed to investigate the maternal thyroid autoimmune status of molar pregnancies. We also compared the maternal thyroid autoantibody positivity of complete and partial molar pregnancies. ABSTRACT