Thyroid Hormone Resistance Syndrome – a Case Report

Clinic of Endocrinology and Metabolic Diseases ,

“Sv. Georgy” University Hospital, Medical University, Plovdiv

 

Abstract:

We describe a case of a 26 year old female with a history of thyroid pathology since the age of 7. In 2007 after a first normal pregnancy and delivery, high levels of FT4 and FT3 with normal TSH and clinical evidence of mild thyrotoxicosis were found. Antithyroid drugs were initiated and during the course of therapy a pronounced increase in TSH was detected along with an enlargement of the goiter. In 2009 thyroidectomy was performed because of the high grade goiter causing compressive symptoms. After the operation a replacement treatment with levothyroxine was initiated but high TSH levels persisted on a dose of 300 μg/d together with elevated FT3 and FT4. The detailed examination revealed a patient in a good general condition with no clinical evidence of thyroid dysfunction. The serum indicators for the action of thyroid hormones on peripheral tissues were within the normal range. MRI data for pituitary microadenoma was present without any evidence of hypersecretion of other pituitary hormones except of TSH. Thyroid hormone resistance syndrome and TSH-producing pituitary tumor were discussed in the differential diagnosis. Genotyping of the patient and her first-degree relatives was performed. A mutation in the hormone-binding domain of the thyroid hormone receptor-β was identified, resulting in the replacement of phenylalanine with cysteine at the codon 451 (F451C). The same mutation and hormonal changes were present in both the father and the sister of the index patient. Moreover, in the three affected members of the family elevated titers of TPOAb were found suggesting an underlying autoimmune thyroid disease. Unawareness of the RTH may lead to an inappropriate treatment, which may aggravate the existing disorder and hamper the treatment and followup of the affected patients.

 

Keywords: thyroid hormone resistance syndrome, autoimmune thyroid disease, thyrotoxicosis