Özsu, ElifYeşiltepe Mutlu, GülÇizmecioğlu, Filiz MineBircan, RifatHatun, Şükrü2022-05-112022-05-1120172147-06342147-0634https://app.trdizin.gov.tr/makale/TWpZek56a3lNZz09https://hdl.handle.net/20.500.11776/6802Subclinical hyperthyroidism is defined as low or undetectable concentration of serum thyrotrophin (TSH) with normal free triiodothyronine (FT3) and free thyroxine (FT4) levels. 1). Familial subclinical hyperthyroidism is a rare entity. Activating mutations of the TSH receptor (TSH-R) gene cause genetic hyperthyroidism. Here we present a family with more than one affected individual. All family members were investigated for TSH-R mutation. No mutation was detected, while a A459 polymorphism was found in one of the cases and three other siblings. Despite the clinical and biochemical findings suggesting a TSH-R mutation, a reasonable cause could not be detected. Epigenetic and environmental modifiers, including iodine intake, should be considered in families with mutation negative, familial non auto-immune hyperthyroidism (FNAH)eninfo:eu-repo/semantics/openAccessGenel ve Dahili TıpArticle61154156TWpZek56a3lNZz09