Insulin-like growth factor I and the development of colorectal neoplasia in acromegaly

Patients with acromegaly are at increased risk of colorectal neoplasia and, by analogy with high-risk nonacromegalic patients, may require regular col onoscopic screening. However, it is unknown whether the risk is equal in al l patients or whether some should be regarded as carrying a particularly hi gh risk. The aims of this study were: 1) to establish the natural history o f colorectal neoplasia in acromegaly; 2) to establish which patients are at increased risk of developing neoplasia; and 3) to elucidate the influence of insulin-like growth factor I (IGF-I) in adenoma formation. A prospective colonoscopic evaluation of the development of new premalignant adenomas in the colon was performed in 66 patients with biochemically proven acromegal y who had previously undergone colonoscopic screening and removal of all vi sible polyps. Twenty-five patients (38%) had a total of 37 polyps detected at the second colonoscopy: nine (14%) had at least one adenoma, and 18 (27% ) had one or more hyperplastic polyps (2 patients had both). The developmen t of new adenomas, but not hyperplastic polyps, was associated both with el evated serum IGF-I (P < 0.005) and, to a lesser extent, with a previous ade noma at the original colonoscopy (P < 0.07). In summary, patients with acro megaly and in whom serum IGF-I remains elevated and/or who have had a previ ous adenoma should be regarded as having an especially high risk for the de velopment of subsequent colorectal neoplasia. Serum IGF-I seems to be impli cated in the development of colorectal neoplasia in acromegaly, although th e exact mechanisms remain uncertain.