Evaluation of Arginine-Nitric Oxide Pathway in Patients with Hyperthyroidism

There is a reciprocal regulation of arginase and nitric oxide synthase in L-arginine metabolizing pathways. Nitric oxide has been claimed as an important role player in hyperthyroidism in recent years. The fact that arginase is an important part of regulation of arginine has not been investigated yet in terms of nitric oxide synthase activity in hyperthyroidism. This study aims to investigate arginase, manganese (a cofactor of arginase) and total nitrite levels (a metabolite of nitric oxide) and their relationship to the arginine- nitric oxide pathway in patients with hyperthyroidism. Arginase activities, manganese, and total nitrite levels were measured in plasma samples from 50 patients with hyperthyroidism and 50 healthy age- and gender-matched control subjects. Plasma arginase activities were found to be significantly lower and total nitrite level higher in patients with hyperthyroidism than those of controls. Manganese levels were not significantly different in hyperthyroidism group compared to those of controls. Our results demonstrate that the arginine-nitric oxide pathway is implicated in the cardiovascular manifestations of hyperthyroidism which may be of clinical relevance.