Iatrogenic Thyrotoxicosis and Corticosteroid-Triggered Hypokalemic Periodic Paralysis in a Patient With Treated Hypothyroidism

Hypokalemic periodic paralysis (HPP) is a rare disorder characterized by episodic weakness with hypokalemia, most commonly associated with thyrotoxic periodic paralysis (TPP) in the setting of endogenous hyperthyroidism. We present a unique case of a 32-year-old male patient with a history of hypothyroidism who developed recurrent episodes of acute paralysis due to iatrogenic thyrotoxicosis from levothyroxine over-replacement. Notably, each episode occurred shortly after corticosteroid administration, suggesting a dual-trigger mechanism. The patient presented with profound, predominantly proximal bilateral extremity weakness with greater upper limb involvement on formal examination (2/5 proximally, an uncommon distribution in TPP) alongside severe hypokalemia (1.8-1.9 mmol/L). Laboratory evaluation revealed suppressed thyroid-stimulating hormone (TSH), and symptoms resolved rapidly with potassium repletion and supportive care. Discontinuation of levothyroxine resulted in clinical stabilization without recurrence during hospitalization. This case highlights an uncommon etiology of TPP due to exogenous thyroid hormone excess and underscores the role of corticosteroids as a potential precipitating factor. Recognition of this interaction is critical for timely diagnosis, prevention of recurrence, and appropriate management. Clinicians should maintain a high index of suspicion for TPP in patients presenting with acute weakness and hypokalemia, even in the absence of known hyperthyroidism.