ESPE Abstracts

Introduction: Thyroid hormone resistance (THR) is a rare syndrome which is characterized by reduced response to thyroid hormones at tissue level. The disorder is caused by genetic mutation in the thyroid hormone receptor. The most common are a heterozygous thyroid hormone β (THRβ) gene mutations. Laboratory tests usually show normal or elevated level of thyroid- stimulating hormone (TSH) and high concentration of thyroid hormones (T3 and T4).

Case report: We present a case of a 10-year-old girl with signs of hyperthyroidism and abnormal thyroid function tests who was hospitalized in Department of Pediatrics, Endocrinology, Diabetology with a Cardiology Division, Medical University of Bialystok. Her physical examination had revealed café au lait spot on abdomen skin, goiter, vascular murmur louder above right lobe of thyroid, tachycardia and heart murmur. In laboratory tests we found elevated serum levels of thyroid hormones: fT3- 14,55 pg/ml (norm: 2,7- 5,2) and fT4- 4,95 ng/dl (norm: 1,1- 1,7 ng/dl) coexisted with normal concentration of TSH -3,64 uIU/l. The thyroid autoantibodies were negative. In TRH stimulating test TSH concentration increased after TRH administration. Sonography revealed normoechogenic, asymetric (right lobe bigger than left) thyroid gland with hypoechogenic 5 x 4 mm area in left lobe, vascular flow was slightly increased in down parts of both lobes. Thin needle aspiration biopsy was performed. Result was benign.

Magnetic resonance imaging (MRI) showed normal pituitary gland and excluded pituitary adenoma. The diagnosis has been confirmed by next- generation sequencing, which exposed a pathogenic variant c.1034G>A in one copy of THR gene. The mutation is known and associated with THR.

Previously patient was given Magnesium, Vitamin D, Vitamin B complex and Propranolol at a dose 10 mg three times a day, which was changed into 20 mg three times a day. She is currently stable on this medication.

Conclusions: Although thyroid hormone resistance is rare, this disorder should be considered in patients with clinical manifestation and thyroid laboratory tests suggested its presence. Mutations of TRβ gene can be seen in various clinical presentations, from isolated bichemical thyroid function abnormalities to thyrotoxicosis or hypothyroidism symptoms. The patients need individualised management.