Thyrotoxic Periodic Paralysis: Eight Cases in Males of Hispanic Origin from a Single Hospital

ABSTRACT Objective: The objective of this study was to present a case series of thyrotoxic periodic paralysis (TPP) in 8 males of Hispanic origin diagnosed at 1 hospital. Methods: This report summarizes the clinical presentations, laboratory values, treatments, and follow-up for a series of patients with TPP. The diagnosis of thyrotoxicosis was based on clinical features and laboratory criteria. The TPP diagnostic criteria were acute muscle weakness, thyrotoxic symptoms, and hypokalemia. Results: All 8 study patients with TPP were Hispanic males ranging in age from 25 to 36 years (mean ± SD, 31 ± 4.4 years). Six patients presented with upper and lower extremity weakness, while 2 patients had only lower extremity weakness. All TPP episodes occurred at night and in the early morning. TPP-associated weakness resolved within 24 hours, either spontaneously or following therapy with potassium chloride (40 to 120 mEq), beta blockers, and methimazole. Six patients had a history of at least 1 previous TPP episode. One patient had an episode 4 weeks after radioactive iodine treatment. Six patients self-reported either drinking large amounts of alcohol or consuming a heavy carbohydrate meal the previous day. In 7 patients, the mean ± SD serum potassium was 2.7±0.7 mEq/L (normal range, 3.5 to 5 mEq/L), ranging from 1.5 to 3.4 mEq/L, with 1 patient measuring 3.9 mEq/L. All 8 patients met the clinical and laboratory diagnostic criteria for thyrotoxicosis, with a mean serum-free thyroxine level of 4.5±1.4 ng/mL (range, 3.2 to 7.7 ng/mL; normal range, 0.58 to 1.64 ng/mL). For 5 patients, this was their first diagnosis of thyrotoxicosis. Thyrotoxicosis was caused by Graves disease (n = 7) or toxic multinodular goiter (n = 1). Among the 6 patients that received potassium chloride treatment, rebound hyperkalemia occurred in 3 patients. All patients received beta blocker and methimazole therapy. Conclusion: To our knowledge this study represents the first large case series of TPP reported in Hispanic males from a single hospital in the United States. TPP is a rare complication of hyperthyroidism. Physician awareness of TPP occurrence in males of Hispanic origin can increase its early recognition and treatment and potentially prevent associated fatalities. Abbreviations: K = potassium KCl = potassium chloride Na+/K+ATPase = sodium-potassium pumps RAI = radioactive iodine TPP = thyrotoxic periodic paralysis T3 = triiodothyronine