Insulin secretion and insulin-like growth factor-I levels in active and controlled acromegaly

We examined the contributions of growth hormone (GH) and insulin-like growth factor-I (IGF-I) to insulin sensitivity and beta-cell function in acromegaly.

A cross-sectional study was used with continuous infusion of glucose with model assessment to determine insulin sensitivity and beta-cell function.

Ten patients with active acromegaly, seven with controlled disease and 22 normal individuals were studied.

Glucose and insulin levels were measured fasting and at the end of the one-hour glucose infusion to calculate insulin sensitivity and beta-cell function. Random GH and IGF-I were recorded. Most patients had values of GH taken after a 100-g oral glucose tolerance test and K values from intravenous glucose tolerance tests. RESULTS Patients with active acromegaly had significantly decreased insulin sensitivity compared to the normal population (P less than 0.001), while those with controlled disease did not. There was a significant negative correlation between IGF-I and insulin sensitivity in those with active disease (P less than 0.05). Beta-cell function in both active and controlled patient groups was elevated compared to the normal population (P less than 0.05, P less than 0.01 respectively) and this was significantly related to IGF-I in the active group (P less than 0.05). GH levels did not correlate with fasting insulin, glucose, insulin sensitivity or beta-cell function in either group.

Patients with active acromegaly have decreased insulin sensitivity and increased beta-cell function that are significantly related to IGF-I but not GH levels. When the disease is controlled, beta-cell function remains elevated but insulin sensitivity improves.