Abstract
INTRODUCTION: Transient congenital hypothyroidism (CH) caused by maternal thyrotropin receptor-blocking antibody (TBAb) has been uncommonly reported. Goiter is a significant indicator of fetal thyroid dysfunction that may facilitate early identification, but some cases present without this manifestation. This report describes a case of CH attributed to maternal elevated levels of thyroid-stimulating hormone receptor antibody (TRAb) with normal thyroid size, and further provides a systematic review of neonatal thyroid size classification in other CH cases from the literature. CASE PRESENTATION: The mother had a history of hypothyroidism related to Hashimoto's thyroiditis and elevated TRAb levels. Maternal TRAb level exceeded 40 IU/L in the first trimester. The circumference of fetal thyroid gland maintained within the normal range throughout pregnancy. However, the secondary ossification centers were not visible at 37 weeks of gestation. CH was confirmed through thyroid function testing on postnatal day 9. Neonatal TRAb levels became undetectable by 3 months after birth, and levothyroxine (LT4) treatment was discontinued at 7 months of age. The young child demonstrated appropriate intellectual development during 18 months of follow-up. We conducted an analysis of 17 TRAb-related CH cases from PubMed, Web of Science and Embase. Most maternal TRAbs (13/17) were detected postpartum, and TBAb levels were measured in nine women with values ranging from 1.13 to 9.94 times of the upper limit of the reference range (ULRR). Neonatal TBAb levels ranged from 1.1 to 8.15 times ULRR. Twelve cases (70.6%) exhibited normal thyroid size, three (17.6%) presented with small thyroids, and two cases (11.8%) displayed goiter. CONCLUSIONS: The majority of TBAb-induced CH cases present with normal thyroid size. In the absence of goiter, monitoring additional signs of hypothyroidism and early evaluation of neonatal thyroid function remain essential. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12884-025-08437-8.