Toxic Thyroid Adenoma Presenting as Apathetic Hyperthyroidism: A Case Report

The thyroid gland is an essential endocrine organ that secretes hormones to regulate homeostasis across multiple organ systems throughout the body. It is actively regulated by the hypothalamic-pituitary-thyroid (HPT) axis, where negative feedback modulates the amounts of active hormone being released; thus, lesions that disrupt the proper functioning of this gland or its regulatory mechanisms can be destructive. Toxic thyroid adenomas are usually singular benign functioning nodules in the thyroid gland that cause thyrotoxicosis. Hyperthyroidism is commonly clinically silent, however, in most symptomatic cases, patients will be diagnosed based on abnormal laboratory findings and typical hyperthyroid symptoms. This case report examines an 81-year-old male with an extensive medical history who presented with complaints of new-onset generalized fatigue coupled with bilateral lower extremity muscle cramps. A positron emission tomography (PET) scan for other medical conditions incidentally noted mildly increased uptake in the thyroid gland, prompting a further investigation that resulted in a diagnosis of toxic thyroid adenoma. The patient responded well to treatment with methimazole and has remained in a euthyroid state.