Glucose intolerance, plasma insulin levels, and colon adenomas in Japanesemen

Hyperinsulinemia may be related to colon carcinogenesis. Several studies ha ve suggested that diabetes mellitus is related to increased risk of colon c ancer. We examined cross-sectionally the relation of fasting plasma insulin levels and glucose tolerance status to colon adenomas. In a consecutive se ries of 951 men undergoing total colonoscopy for a health examination at th e Japan Self Defense Forces Fukuoka Hospital from April 1998 to August 1999 , we identified 233 cases of colon adenomas and 497 controls with normal co lonoscopy. Glucose tolerance status was determined by a 75-g oral glucose t olerance test, and subjects were classified as normal, impaired glucose tol erance (IGT) or non-insulin dependent diabetes mellitus (NIDDM). Plasma ins ulin levels were measured after subjects had fasted overnight. Logistic reg ression analysis and analysis of covariance was used to control for age and obesity. While plasma insulin levels were unrelated to colon adenomas, NID DM was associated with a significantly increased risk of colon adenomas. Th ere was no association between IGT and colon adenomas. NIDDM was more stron gly associated with proximal colon adenomas. The findings suggest that long -term hyperinsulinemic status associated with NIDDM may increase the risk o f colon adenomas, and subsequently of colon cancer.