Endocrine Abstracts

Elevated insulin levels are correlated with colonic adenomas and carcinomas in the general population. Patients with acromegaly are considered at high risk to develop colonic lesions and have a high insulin levels. To evaluate the role of insulin levels on colonic polyps (hyperplastic, adenomatous, single or synchronous) or adenocarcinoma in acromegaly we designed this analytical, observational, open, prospective, study enrolling 189 patients (100 women, 89 men, age 20–82 yrs) undergoing pan-colonoscopy at diagnosis. Age, gender, estimated disease duration, body mass index, GH and IGF-I levels, fasting glucose and insulin levels, HOMA-index [R (resistance) and β (β-cell function)] were considered as predictors. Colonic lesions were found in 74 patients (39.1%): hyperplastic polyps in 31 (16.4%), adenomatous polyps in 24 (12.7%), both hyperplastic and adenomatous polyps in 14 (7.4%) and adenocarcinoma in 6 patients (3.2%); polyps were single in 22 patients (29.8%) and synchronous in 52 (70.3%). Colonic lesions were positively correlated with patients’ age, insulin levels, HOMA-R and HOMA-β (P<0.0001), negatively with GH levels (P=0.006) but not with estimated disease duration, IGF-I levels, BMI or glucose levels. Compared to patients with normal glucose tolerance, patients with impaired glucose tolerance had a prospective risk (RR) to develop colonic lesions 2 times higher (95% CI 1.2–3.3) while those with diabetes 2.9 times higher (95% CI 1.8–4.6). Serum fasting insulin levels were the strongest predictor of the presence of colonic lesions. The best cut-off of insulin levels to predict the presence of colonic lesions was 20.6 mUI/liter [sensitivity=73.8% (61.5–84%); specificity=81.1% (72.5–87.9%); positive predictive value=69.6%, negative predictive value=84.1]. The patients with fasting insulin levels >20.6 mU/liter at the diagnosis of acromegaly had a RR to develop colonic lesions 5.1 times higher than those with levels ≤20.6 mU/liter (95% CI 3.1–8.5). In conclusion, high fasting insulin levels predict the presence of adenomas and adenocarcinomas.