[Effect of thyroxine on the adaptive potentials of the pancreatic islet system beta cells]

Functional activity of the pancreatic insulin-producing apparatus during long-term administration of thyroxin high doses was studied in experiments on mature male rabbits. Thyroxin decreased secretory response of beta-cells to glucose when intravenous glucose tolerance test was carried out and to be lesser degree when peroral glucose tolerance test was realized (insulin level in the peripheral blood plasma at various times after glucose injections was significantly lower than in control animals). Carbohydrate tolerance remained unchanged. It retained the hyperglycemic reaction pattern similar to that developing after the infection of guinea-pig antiinsulin serum. An elevation of the sugar-decreasing effect of exogenous insulin was typical.