Intravenous Iodinated Contrast Induced Thyrotoxic Periodic Paralysis: A Case Report

Thyrotoxic periodic paralysis (TPP) is an entity that has been described in the literature as a transient, symmetrical, flaccid paralysis, mainly affecting the lower limbs of patients with a current or previous history of hyperthyroidism. In most cases, Graves' disease is the cause of hyperthyroidism. Contrast and iodine-induced TPP have been described in the literature, but only one case of intravenous contrast induced TPP has been reported. We report a case of TPP following administration of intravenous contrast for a computed tomography scan of the neck prior to lymph node excision. A 35-year-old Kuwaiti male with known Graves' disease in remission until two months of his presentation, reported to the emergency room one early morning in December 2020. He sustained a fall from the stairs due to bilateral lower limb weakness, mostly proximal. The upper limbs were spared, and the patient did not experience any numbness or headache. His potassium was found to be 2.1 mmol/L and an electrocardiogram showed U waves and ST segment changes. He was initiated on 20 mEq of intravenous potassium chloride in 500 mL sodium chloride over one hour, following which his potassium approached normal and his weakness resolved. He was last known to be euthyroid in November 2019 but noted in October 2020 to be in the hyperthyroid state when thyroid function testing showed a thyroid-stimulating hormone of <0.005 (0.27-4.2 uIu/mL) and free thyroxine (T4) of 27.6 (7.8- pmol/L). In patients with known hyperthyroidism, more caution is required when iodine-containing substances are administered without proper evaluation of thyroid function.