Endocrine Abstracts

A 30-year-old man of Asian descent presented to the emergency department with recurrent episodes of sudden onset limb weakness and difficulty walking over a period of 3 years. Each episode resolved within 2–3 h and he had fully normal mobility in between episodes. He denied any visual, bulbar symptoms or other focal neurology.

He had a 9 year history of Graves’ disease for which he had recently discontinued carbimazole therapy in preparation for radio-iodine treatment. He had been extensively investigated for these episodes of weakness, as an outpatient by the neurology team, with normal head and whole spine magnetic resonance imaging and nerve conduction studies.

Upon further questioning, the patient stated that these episodes coincided with instances when his thyroid state was not fully controlled and most commonly first thing in the morning. On examination, he was found to have reduced power in all four limbs with the proximal lower limbs most affected. No other abnormal neurology was elicited.

Routine blood tests on this admission identified that the patient was hypokalaemic and thyrotoxic with serum potassium 2.1 mmol/l, phosphate 0.44 mmol/l, free thyroxine (FT₄) 44 pmol/l and free tri-iodothyronine (FT₃) 40.4 pmol/l. ECG showed sinus tachycardia. A diagnosis of thyrotoxic periodic paralysis was made and he was treated with oral and intravenous potassium replacement, propranolol and carbimazole and discharged the next day when his serum potassium levels returned to normal.

This case highlights this lesser considered feature of thyrotoxicosis and is a reminder that an atypical presentation can delay diagnosis, which can be frustrating for the patient and the clinician. This patient was seen by neurologists and had multiple admissions before the correct diagnosis was considered. Careful attention to the patient’s description of their illness as well as comorbidities may aid earlier diagnosis.