The association of fasting insulin concentrations and colonic neoplasms in acromegaly: a colonoscopy-based study in 210 patients.

CONTEXT

Hyperinsulinemia is associated with colon carcinoma in the general population. PATIENTS with acromegaly are considered to be at risk for developing colonic lesions and typically have hyperinsulinemia.

OBJECTIVE

Our objective was to evaluate the role of fasting insulin levels on the prevalence of colonic adenomatous polyps or adenocarcinoma in acromegaly.

DESIGN

This is an analytical, observational, prospective study.

PATIENTS

A total of 210 patients (111 women, 99 men, age 20-82 yr) undergoing complete colonoscopy at diagnosis of acromegaly were included in this study.

RESULTS

Colonic lesions were found in 81 patients (38.6%), and consisted of hyperplastic polyps in 33 (15.7%), adenomatous polyps in 42 (20.0%), and adenocarcinoma in six patients (2.8%). Polyps were single in 22 cases (27.1%). Fasting insulin levels were significantly lower in patients without lesions (16.0 +/- 7.5 mU/liter) than in patients with hyperplastic polyps (22.4 +/- 8.8 mU/liter; P < 0.01), adenomatous polyps (38.0 +/- 15.9 mU/liter; P < 0.0001), and adenocarcinoma (59.0 +/- 30.6 mU/liter; P < 0.0001). Fasting insulin levels were also lower in patients with hyperplastic polyps than in those with adenomatous polyps (P < 0.01). The odds ratio for harboring colonic adenomas was 14.8 (95% confidence interval 4.4-51.2; P < 0.0001) and 8.6 times higher (95% confidence interval 2.8-29.0; P < 0.0001) in patients with fasting insulin levels in the upper tertile [>/=27.1 mIU/liter (n = 28)] compared with the lower [</=12.1 mIU/liter (n = 40)] and middle tertiles [>12.1 to <27.1 mIU/liter (n = 74)], respectively.

CONCLUSION

An increase in fasting insulin levels is associated with an 8.6- to 14.8-fold increased risk of presenting with colonic adenomas in acromegaly.