Myxedema Coma Despite Mild Biochemical Hypothyroidism: A Case of Profound Clinical Decompensation

Myxedema coma is a rare endocrine emergency with high mortality that is typically associated with severe biochemical hypothyroidism. However, profound clinical decompensation may occur despite only modest abnormalities in thyroid function tests, making diagnosis challenging. We report the case of an 87-year-old woman with long-standing hypothyroidism, primary adrenal insufficiency, pituitary pathology, and ischemic heart disease who presented with an Escherichia coli urinary tract infection and subsequently developed profound hypothermia, severe bradycardia, hypotension, reduced consciousness, and gastrointestinal hypomotility despite appropriate antimicrobial therapy. Thyroid function tests demonstrated only mildly elevated thyroid-stimulating hormone with near-normal free thyroxine concentrations. Repeat clinical assessment revealed delayed relaxation of the ankle reflexes. Retrospective application of the Popoveniuc diagnostic scoring system gave a score of 105, providing strong support for the diagnosis of myxedema coma. The end-of-life care pathway was reversed, and treatment with intravenous hydrocortisone, intravenous levothyroxine, active warming, and supportive care resulted in marked clinical recovery. This case highlights the importance of recognizing myxedema coma as a clinical diagnosis, maintaining a high index of suspicion despite relatively mild biochemical abnormalities, and undertaking repeated clinical reassessments in elderly patients with impaired endocrine reserve.