Unmasking Hypokalemic Periodic Paralysis: The Rare Role of Levothyroxine in a Pakistani Woman

Levothyroxine-induced thyrotoxic hypokalemic periodic paralysis belongs to a rare group of periodic paralysis that lead to sudden onset of weakness in proximal muscles. Thyrotoxic periodic paralysis (TPP) is a common manifestation among East Asian patients with hyperthyroidism but is infrequent among the South Asian population. To highlight levothyroxine as a major contributor to periodic paralysis and the importance of frequent monitoring of serum potassium levels in patients taking levothyroxine, necessary to prevent life-threatening complications such as neuromuscular paralysis.

Patient presented as outpatient with chief complaints of generalized muscle weakness and myalgias more pronounced in the proximal muscles of the upper and lower extremities for 3 months. Biochemical investigations revealed a low serum potassium level of 2.8 mEq/L with no other known medical or surgical illness of note. However, the patient had previously been admitted to the intensive care unit for acute periodic paralysis, which resolved with potassium supplementation and was later linked to a high dose of levothyroxine for her hypothyroidism.

This case report discusses TPP triggered by levothyroxine overreplacement, presenting as acute flaccid paralysis with hypokalemia. While similar to familial periodic paralysis, it differs in cause, age of onset, and genetic patterns. Timely diagnosis and management can reverse the condition effectively.

This case contributes to the growing body of knowledge regarding the timely dose adjustments of levothyroxine and potential genetic and ethnic risk factors that contribute to TPP, and emphasizes that immediate resuscitation measures, such as potassium supplementation, can prevent rare but potentially fatal complications.