Thyroid-Stimulating Antibodies and Thyroid Stimulation-Blocking Antibodies During the Pregnancy and Postpartum Period: A Case Report

This report describes a unique pattern of changes in thyroid function and thyroid antibodies in a woman during the course of two pregnancies and two postpartum periods. A 25-year-old woman developed hypothyroidism in the postpartum period after the delivery of her first child. She was found to have potent thyroid stimulation-blocking antibodies (TSBAb) in the serum. One year later, she became pregnant again, and during the pregnancy, TSBAb had decreased to an undetectable level. She gave birth to the second healthy child and developed postpartum thyrotoxicosis, probably due to destruction of the thyroid gland, which gradually resolved. In this postpartum period, serum TSBAb levels increased. Eight months postpartum, she developed what appeared to be Graves' disease with an elevated ¹²³I-thyroid uptake. Serum thyroid-stimulating antibodies (TSAb) were found at that time, and the TSBAb had disappeared from her serum.