Insulin and gall stones: a population case control study in southern Italy

Background-Hyperinsulin aemia has been associated mith many common diseases in developed countries, such as ischaemic heart disease and colon cancer. Gall stones are also very prevalent in these countries but little is known about the association between insulin and gall stones. Aims-To study the relationships between insulin and the incidence of gall s tones in a sample of the general population. Subjects and methods-Between May 1985 and June 1986, systematic sampling fr om the electoral register of Castellana, a small town in southern Italy, yi elded 2472 subjects who had their gall bladder checked for gall stones by u ltrasonography. Between May 1992 and June 1993, 1962 of the 2235 subjects w ithout gall stones at the first examination agreed to a further ultrasound examination. A total of 101 subjects with newly diagnosed gall stones and 3 03 randomly chosen controls entered the study. Serum insulin was determined by radioimmunoassay, and concentrations of cholesterol, cholesterol high d ensity Lipoprotein (HDL), glucose, and triglycerides by standard enzymatic colorimetric methods. Unconditional multiple logistic regression was used t o study the association between insulin and gall stones, controlling for th e most common confounding factors. Results-In individuals with no clinical diagnosis of diabetes and serum glu cose <7 mmol/l, insulin was associated with gall. stones. This association persisted even after controlling for sex, age, body mass index, and serum g lucose. The risk of gall stones in the highest quintile of serum insulin wa s 2.66 (95% confidence interval 1.04-6.721 chi(2) test for trend, p=0.03). The association of insulin with gall stones persisted when total and HDL ch olesterol were entered in the logistic regression models, and only slightly decreased when serum triglycerides were included in the model. Conclusions-The results of the study indicate that hyperinsulinaemia may pl ay an important role in the aetiology of gall stones even in individuals wi thout diabetes and with normal serum glucose levels.