[Role of high blood glucagon in the reduction of serum levels of triiodothyronine in severe non-thyroid diseases].

In healthy subjects intravenous glucagon administration induces a prompt (at 1 h) fall in serum T3 concentration and a later (at 4 h) rise in biologically inactive rT3. Since high levels of plasma glucagon have frequently been found in some patients with severe chronic illnesses, together with an anomalous thyroid condition (low serum T3, high serum rT3), it has been supposed that hyperglucagonemia could play a pathogenetic role in causing selective T3 deficiency. In the present study fasting plasma glucagon concentration was measured in 48 patients with low T3 and severe nonthyroidal illnesses: hepatic cirrhosis in 16 cases, chronic non-A non-B hepatitis in 4 cases, uncontrolled type II diabetes mellitus in 5 cases, renal failure in 12 cases, congestive heart failure in 5 cases, tumor in 16 cases. In comparison with a group of 21 healthy controls fasting plasma glucagon concentration was significantly higher in the patients (198.75 +/- 13.20 pg/ml vs. 127 +/- 6.80 pg/ml; p less than 0.001). However, only 29 patients (60.4%) had elevated plasma glucagon levels, whereas 19 (39.5%) had abnormal plasma glucagon levels. Furthermore, no significant difference was found between the thyroid hormone pattern of the patients with hyperglucagonemia and of the patients with normal glucagonemia. On the other hand, a significant correlation between plasma glucagon concentrations and serum T3 and rT3 concentrations was not found. All these findings indicate that in patients with severe chronic illnesses the fall in circulating T3 cannot be due to hyperglucagonemia only which, therefore, might simply be a contributory factor together with other as yet unidentified disorders.