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.