Case Report.

Background Thyroid hormone resistance (RTH) is defined as a decrease in response to thyroid hormones in the target tissue. Most patients present with nonspecific findings. In this article, we aimed to represent a 22-year-old female patient who presented with palpitation, fatigue, and heat intolerance. She was thought to have thyroid hormone resistance and her genetic examination revealed NM_001128177.1 (THRβ): c.1034G > A (p.Gly345Asp) pathogenic variation in the THRβ gene. Case report A 22-year-old female patient presented with complaints of fatigue, heat intolerance and palpitations. She was taking Propranolol twice daily at admission. Her family history revealed hypothyroidism in her grandmother. Her physical examination results were as follows: height 160 cm, weight 65 kg, body mass index 25.4kg/m2, body temperature 36.5°C, respiratory rate 18/min, heart rate 86 beats/min, blood pressure 120/80 mmHg. Her palms were sweaty. The heart sounds were normal, and no heart murmur was auscultated. The laboratory results were TSH: 5.31uU/mL, fT3: 6.83 pg/mL, and fT4: 2.43 ng/dL. THRβ gene mutation analysis was requested for our patient whose clinical history and laboratory results were compatible with thyroid hormone resistance. The pathogenic variation NM_001128177.1(THRβ):c.1034G>A (p.Gly345Asp) was detected after analysis. Conclusion A diagnosis of RTH requires high clinical suspicion and a genetic mutation analysis should be requested in the case of clinical suspicion. In this way, unnecessary anti-thyroid treatment can be prevented.