THRB and attention deficit-hyperactivity disorder: Since TRβ isoforms are expressed in few tissues, the RTHβ patients exhibited tissue-specific hypothyroid-related defects such as hepatic steatosis, dyslipidemia, and impaired hearing and color vision, together with thyrotoxic manifestations including attention-deficit hyperactivity disorder (ADHD), anxiety, tachycardia, and low bone density (53–55).