Studies on the Effect of Combined Growth Hormone and Cortisol on the Insulin Response to Glucose in the Hypophysectomized Dog[*]

Abstract

Serum immunoreactive insulin concentrations during a glucose tolerance test were measured in hypophysectomized and normal dogs, before and after growth hormone and Cortisol combined therapy. Growth hormone (0.03 mg/kg body weight/ day) was given during the last five days of Cortisol regimen (1.0 mg/kg body weight/day for 15 days). These hormone doses were within the physiological range. The last hormone injection was given one hour before the glucose tolerance test was begun. Dogs received a rapid I V infusion of glucose (1 gm/kg body weight) for glucose tolerance test.

The results obtained show that growth hormone and Cortisol combined therapy produces a striking increase in the insulin response to glucose in hypophysectomized dogs. In normal dogs, the character of the insulin response to glucose was normal, increasing two-fold over base line levels, which were twofold increased after hormone therapy. Serum immunoreactive insulin returned to post-absorptive levels before 45 minutes following glucose load in both hypophysectomized and normal dogs under therapy. Serum immunoreactive insulin concentration in hypophysectomized dogs in the post-absorptive state was not changed after therapy.

Glucose levels during the glucose tolerance test in normal dogs were unaffected by hormone treatment. A slight decrease in mean glucose without any change in Conard's k constant was found in the hypophysectomized group after therapy. A mild degree of insulin resistance was detected in dogs after growth hormone plus Cortisol regimen.

Key words

Hypophysectomized Dogs - Glucose Tolerance Test - Growth Hormone plus Cortisol Therapy - Serum Immunoreactive Insulin - Insulin: Glucose Ratio

1 This work was partially supported by Research Grant No. 2304-B from the Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina) and by a Research Contract from the Comision Nacionale de Energía Atómica (Argentina).

1 This work was partially supported by Research Grant No. 2304-B from the Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina) and by a Research Contract from the Comision Nacionale de Energía Atómica (Argentina).