Endocrine Abstracts

JOINT389

Case Presentation: A 20-year-old male patient, of south american and oriental descent, presented in January 2024 with sudden onset of muscle weakness and flaccid paralysis of the lower limbs, progressing rapidly to upper limb plegia, while respiratory movements remained preserved. Initial examination revealed hypertension (BP > 140/90 mmHg), sinus tachyarrhythmia (ECG), and severe hypokalemia (K: 2.8 mEq/l). The patient was admitted to the Intensive Care Unit for potassium repletion, during which transient hyperkalemia occurred, but was resolved without serious consequences. After normalization of potassium (4.1 mEq/l), the patient was discharged. Approximately 30 days later, the patient experienced another episode of lower limb weakness and hypokalemia, prompting further investigation. Laboratory tests revealed hyperthyroidism (TSH: <0.008 µUI/ml, T4: 5.14 ng/dl, T3: 17.9 ng/dl) and elevated anti-thyroid antibodies. A diagnosis of hyperthyroidism was confirmed, and treatment with methimazole (30 mg/day) was initiated. After 90 days, follow-up tests showed improved thyroid function (TSH: 0.01 µUI/ml, T4: 1.12 ng/dl, TRAB: 1.51 U/l). Thyroid ultrasound showed a normal-sized gland with no solid or cystic lesions. The patient remains asymptomatic with no further episodes of tachycardia, hypokalemia, or paralysis.

Discussion: Hypokalemic periodic paralysis (HPP) is a rare complication of hyperthyroidism characterized by a triad of hypokalemia, thyroid dysfunction, and skeletal muscle paralysis. Episodes of HPP are often transient and can affect the lower limbs, occasionally progressing to the upper limbs. The condition is precipitated by high carbohydrate intake or intense physical activity and often occurs during the night or upon awakening. Thyroid symptoms can be subtle, with diagnosis confirmed through laboratory tests. In the electrocardiogram, signs of HPP include sinus tachycardia, ST-segment alterations, T-wave flattening, prolonged QT intervals, and in severe cases, ventricular fibrillation. Treatment involves controlling hyperthyroidism with antithyroid drugs, iodotherapy, or thyroidectomy. In acute episodes, careful potassium repletion and beta-blockers are essential to prevent recurrence.

Conclusion: Although rare, hypokalemic periodic paralysis (HPP) in the context of hyperthyroidism must be recognized promptly by clinicians. With increasing numbers of individuals of Asian descent in the world, understanding the pathophysiology and epidemiology of this condition is crucial for early diagnosis and treatment, which can prevent severe complications, including respiratory failure and death.