Changes of Carbohydrate Tolerance in Acromegaly with Progress of the Disease and in Response to Treatment

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Abstract
This study was planned to investigate the pathogenesis of diabetes in acromegaly. Standard intravenous glucose tolerance tests were done with measurements of blood sugar, plasma insulin, growth hormone and free fatty acids. Sixteen patients were studied, and 10 had more than one glucose tolerance test. Seven of the patients had impaired carbohydrate tolerance, including 2 with symptomatic diabetes. In 6 patients serial tests showed the change that may occur as carbohydrate tolerance deteriorates, and in 5 the response to surgical hypophysectomy was observed. Fasting hyperinsulinism was present in 6, and insulin response to intravenous glucose was increased in 10. The pattern of this response varied—in 10 there was a peak in the first 15 min, in 4 the pattern resembled that of maturity onset diabetes, with a gradual rise of plasma insulin concentration toward a peak at 60 min. In the 2 patients with symptomatic diabetes, there was no response to intravenous glucose although the fasting plasma insulin was increased. One patient with an invasive pituitary tumor was followed for 2 yr while normoglycemia with hyperinsulinism developed into symptomatic diabetes with a flat plasma insulin curve. In another patient, improved carbohydrate tolerance after operation was associated with return of the plasma insulin response to normal. In most patients with active acromegaly the apparent glucose space was found to be increased, with a tendency to fall after successful surgical treatment.