Triiodothyronine (T₃) Toxicosis with Hypokalemic Periodic Paralysis

Abstract

A case of triiodothyronine (T₃) toxicosis associated with hypokalemic periodic paralysis is reported. Thyrotoxic manifestation was minimal except for mild struma. Serum T₃ levels were moderately elevated, though other thyroid function tests were within the normal range. The patient was treated with methimazole, and paralytic attacks ceased. This is the first report of this combination and the necessity of careful thyroid function tests in sporadic periodic paralysis is emphasized.

Normokalemic Thyrotoxic Periodic Paralysis: A New Therapeutic Strategy

“…The patient in this case never developed hypokalemia and presented long-term flaccid paralysis that improved rapidly with the administration of glucocorticoids (as was later recognized). As other authors have commented, the levels of free T3 and T4 can be used to monitor euthyroidim and thus avoid relapses (8,9). The case reaffirms that the factors causing paralysis are directly related to T4 and T3 levels (4).…”

Thyrotoxic Hypokalemic Periodic Paralysis: Report of Four Cases in Black American Males1

“…As the hypokalemia is corrected with potassium replacement, the muscle weakness improves in the reverse order of the appearance of the weakness. Although elevation of CPK has been noted in some case reports, the majority of case reports do not comment on this lab abnormality (5,15,17,19,23,33). The significance of the elevation is probably related to the hypokalemia and muscle weakness but very little is found in the literature regarding this abnormality.…”

“…The etiology of hyperthyroidism in patients with TPP is most commonly Graves' disease, as in our four cases, but can be due to almost any other cause of thyrotoxicosis. Most exhibit elevated serum levels of T4 and T3 with a suppressed TSH; however, reports of TPP in patients with thyrotropin-secreting tumor (4), T3 toxicosis (1,5), toxic multinodular goiter (6), toxic adenoma (1), iodine-induced thyrotoxicosis (2,3,7), and lymphocytic thyroiditis have been documented. In our four cases, one patient (Case 3) already carried a diagnosis of Graves' disease and the other three patients had clinical and biochemical evidence of hyperthyroidism on presentation but no prominent history of hyperthyroid symptoms.…”

“…It is most commonly a complication of Graves' disease but can occur with any etiology of thyrotoxicosis (1)(2)(3)(4)(5)(6)(7). Despite a higher incidence of thyrotoxicosis in women, TPP is more frequently observed in men than women (8,9).…”