Drug-induced thyrotoxic periodic paralysis.

OBJECTIVE: To report a case of iodine-induced (Jod-Basedow) hyperthyroidism leading to thyrotoxic periodic paralysis (TPP).

CASE SUMMARY: A 64-year-old white male, one day status-post-cardiac catheterization, presented to the local emergency department with profound weakness of his extremities and an inability to stand on his own. Pertinent laboratory test results included a potassium level of 3.0 mEq/L. Treatments of oral and intravenous potassium supplementation resulted in his complete recovery. Two days later he was diagnosed with hyperthyroidism and subsequently treated with nadolol 40 mg daily and methimazole 20 mg daily. At time of writing, the patient remained euthyroid, receiving no antithyroid medications. There had been no further reports of paralysis in the 6 years since his original presentation. The Naranjo probability scale indicated a probable relationship between the patient's episode of TPP and his exposure to the iodinated contrast dye.

DISCUSSION: TPP is an uncommon manifestation in white patients with hyperthyroidism. Iodine-induced TPP is even more rare, with only 2 such cases reported as of November 2, 2005. In this case, Jod-Basedow hyperthyroidism was induced by the iodine-containing dye that the patient received during cardiac catheterization. Soon after the dye was administered, he developed TPP.

CONCLUSIONS: Clinicians should be aware not only of potential causes of drug-induced thyroid disease, but also of the potential for drug-induced hyperthyroidism leading to TPP. The diagnosis of TPP should be considered in patients presenting with acute onset of extremity weakness or paralysis and hypokalemia. Quick diagnosis and prompt treatment of TPP can prevent life-threatening complications of this treatable and curable disorder.