Circulating glucagon to ghrelin ratio as a determinant of insulin resistance in hyperthyroidism

Abstract

Due to stimulated overall metabolism, a state of nutritional inadequacy often ensues, during thyrotoxicosis. We aimed to investigate circulating levels of some major components of the system that regulates energy stores, glucose, and fat metabolism, during thyrotoxicosis compared to euthyroidism. Fasting serum ghrelin, leptin, adiponectin, insulin, glucagon, glucose, as well as body fat composition were analyzed during thyrotoxicosis in 40 hyperthyroid patients (50.5 ± 15.2 years old, 22 females, 31 with Graves disease, and 9 with toxic nodular goiter). The same measurements were repeated an average 3 months later, when all patients achieved euthyroidism. Compared to euthyroidism, in thyrotoxicosis, patients had lower ghrelin and fat mass; had comparable insulin, HOMA-IR, glucagon, and leptin levels; higher levels of circulating adiponectin. Fasting serum glucose tended to be higher during thyrotoxicosis. The unique correlation of HOMA-IR was with the-glucagon to ghrelin ratio-(r = 0.801, p < 0.001) in hyperthyrodism, and with glucagon itself in euthyroidism (r = -0.844, p < 0.001). Circulating levels of ghrelin are decreased; leptin, insulin, glucagon are unchanged; adiponectin are increased during hyperthyroidism. The fasting HOMA-IR tends to be higher, despite the decreased adiposity in hyperthyroidism. The-glucagon to ghrelin ratio-strongly correlates with fasting HOMA-IR in hyperthyroidism.