Fetal hyperthyroidism is a rare prenatal disease and can be life-threatening. The diagnosis is based on ultrasound in mothers with a history of Basedow–Graves' disease and elevation of thyrotropin receptor antibodies (TRAbs) levels. The treatment consists of antithyroid drugs. We present a mother with Basedow–Graves' disease, treated with radioactive iodine 16 years ago. She had an unplanned pregnancy at the age of 29 years, and an elevation of TRAbs (21 U/L) was found at the sixth week of pregnancy. At 22 weeks of gestation, fetal ultrasound displayed tachycardia, goiter, exophthalmos, and suspicion of craniosynostosis, hence methimazole was started. Concomitantly, suppressed maternal thyroid-stimulating hormone (TSH) was found. Her daughter was born at 33 + 6 weeks showing clinical and laboratory findings of hyperthyroidism. Consequently, treatment with methimazole was prescribed. Normal thyroid function was documented in the mother after giving birth. Clear explanation has not been found for the alteration of maternal TSH during pregnancy.

Received: 12 October 2022

Accepted: 10 April 2024

Accepted Manuscript online:
02 May 2024

Article published online:
31 May 2024

© 2024. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)

Thieme Medical Publishers, Inc.
333 Seventh Avenue, 18th Floor, New York, NY 10001, USA