A 15-year-old young girl was found dead at home. There were no indications of any intervention or the application of force. On the previous day, she was admitted to hospital because of palpitations, fatigue, a headache, and a swollen neck. During a physical examination, a swollen thyroid gland and tachycardia were found. In the family history, her mother had thyroid disease. According to the laboratory values, she had elevated thyroid hormone levels. After administration of beta-blockers, the patient was discharged and died at home during the night. The parents denounced the hospital for medical malpractice; therefore, a Forensic Autopsy was performed. Based on the available clinical data, the autopsy, histological and toxicological results, the cause of death was stated as multiorgan failure due to disseminated intravascular coagulation (DIC) caused by the autoimmune Graves disease. The forensic assessment of the case does not reveal medical malpractice. Post-mortem diagnoses of thyroid disorders in cases of sudden death can be challenging. However, as the reported case illustrates, the diagnosis could be established after a detailed evaluation of antemortem clinical data, autopsy results, histology, and a toxicological examination.