Hyperinsulinaemia as a risk factor for developing benign prostatic hyperplasia

Objective: To determine the validity coefficient of the total prostate glan d volume as an expression of the transition zone (TZ) volume. To test the h ypothesis of hyperinsulinaemia as a causal factor for the development of be nign prostatic hyperplasia (BPH). Patients and Methods: Three hundred and seven consecutive patients with low er urinary tract symptoms were studied. A subgroup of 114 patients were tes ted with regard to the validity coefficient between the total prostate glan d volume and the TZ volume. In the total material of 307 men, a BPH risk fa ctor analysis was performed in which groups of men with the following condi tions were related to the annual BPH growth rate: men without or with metab olic disease; men with different components of the metabolic syndrome, and men with low or high fasting plasma insulin values. The prostate gland volu me and the TZ volume were determined using ultrasound. The presence of non- insulin-dependent diabetes mellitus (NIDDM) and treated hypertension was ob tained from the patients' medical records. Data on blood pressure, waist an d hip measurement, body height and weight were collected and body mass inde x and waist/hip ratio were calculated. Blood samples were drawn from fastin g patients to determine the insulin and HDL-cholesterol values. Results: In the subgroup of men subjected to measurement of both the total prostate gland volume and the TZ volume, the correlation coefficient betwee n total prostate gland volume and the TZ volume was r.s. =0.97 (p<0.0001) w hich, thus, constituted the validity coefficient. The median annual BPH gro wth rate in the total group was 1.03 ml/year. The median annual BPH growth rate was faster in men with metabolic disease (p<0.0001), NIDDM (p<0.0001), treated hypertension (p<0.0001), obesity (p<0.0001) and dyslipidaemia (p<0 .0001) than in men without metabolic disease. Moreover, the annual BPH grow th rate correlated positively with the diastolic blood pressure (r.s. = 0.2 7; p<0.001), the BMI (r.s. = 0.22; p<0.001) and four other expressions of o besity, and negatively with the HDL-cholesterol level (r.s. = -0.15; p<0.00 1). The methan annual BPH growth rate was faster in men with a high than in men with a low fasting plasma insulin level (p = 0.019). When the patients were divided into quartiles, the median annual BPH growth rate increased s tatistically significantly with increasing fasting plasma insulin levels. T he fasting plasma insulin values correlated with the annual BPH growth rate s (p = 0.009). When performing a multivariate analysis using the total pros tate gland volume as dependent variable, fasting plasma insulin (p = 0.001) and age (p<0.001) became statistically significant. Conclusion: The results of the present report suggest that the total prosta te gland volume constitutes a valid expression of BPH. The findings support the hypothesis that hyperinsulinaemia is causally related to the developme nt of BPH and generate the hypothesis of an increased sympathetic nerve act ivity in men with BPH. Copyright (C) 2001 S. Karger AG, Basel.