Syndrome of inappropriate secretion of thyrotropin: Differential diagnosis / 中华内分泌代谢杂志

ABSTRACT

Objective:Through comprehensive analysis of symptoms and signs, biochemistry, imaging, and dynamic tests, to explore the diagnosis and differential diagnosis of thyrotropin-secreting pituitary adenoma(TSH adenoma) and syndrome of resistance to thyroid hormone(RTH).Methods:A retrospective analysis was conducted on clinical data from 14 patients who visited the First Affiliated Hospital of Zhengzhou University from July 2016 to September 2022, exhibiting elevated levels of free thyroxine(FT4) and free triiodothyronine(FT3) in the presence of increased TSH.Results:There were 7 cases of TSH adenoma and 7 cases of RTH, with the average age of diagnosis at 40.0 years and 26.6 years, respectively. Thirteen patients showed thyrotoxicosis or occasional palpitation, some with pituitary occupancy manifestations or abnormal growth and development; One patient presented with neck thickening. Sex hormone binding globulin was elevated in 3 cases of TSH adenoma. Pituitary magnetic resonance imaging showed that all 7 cases of TSH adenoma were macroadenomas and 1 case of RTH was microadenoma. The octreotide suppression test in 13 patients was inhibited, but there was a significant difference in the inhibition rate of 24 h/2 h TSH inhibition rate of TSH adenoma and RTH, ranging from 46.6% to 83.9% and 4.6% to 28.8% respectively. Six cases of RTH had thyroid hormone receptor β mutation.Conclusion:Syndrome of inappropriate secretion of thyrotropin is a rare condition, mainly including TSH adenoma and RTH. The diagnosis and differentiation of the two conditions require comprehensive assessment incorporating family history, symptoms and signs, laboratory tests, dynamic test, and genetic test. Among these, the 24 h/2 h TSH inhibition rate of octreotide suppression test can effectively distinguish TSH adenoma from RTH.