Lower Extremity Cramping and Palpitations in a 17-Year-Old Boy

A 17-year-old boy with obesity and no routine pediatric care presented with symptoms of muscle fatigue, cramping, palpitations, and weight gain. Initial tests showed elevated creatine kinase and creatinine levels, leading to a diagnosis of severe hypothyroidism secondary to Hashimoto’s disease. This condition caused myopathy, rhabdomyolysis, acute kidney injury (AKI), and bradycardia. Treatment with intravenous levothyroxine and liothyronine improved his symptoms, and he was discharged on oral levothyroxine. Despite normalization of thyroid hormone levels and heart rate, the patient continued to experience occasional palpitations, which were not linked to his treated hypothyroidism. His creatinine levels normalized after treatment, and he lost 20 kg over 5 months.