Increasing abdominal obesity and serum leptin levels are associated with increased prostate volume, according to a new study.

Jae Hung Jung, MD, of Yonsei University Wonju College of Medicine in Wonju, Korea, and colleagues studied 571 men who underwent urologic examination, including serum PSA measurement and transrectal ultrasonography, and completed the International Prostate Symptom Score questionnaire. Men with a mean prostate volume of less than 30 mL, at least 30 but less than 40 mL, and 40 mL or more (high-volume benign prostatic hyperplasia, BPH) had a mean waist circumference of 86.62, 87.45, and 89.80 cm, respectively; mean body mass index (BMI) of 24.38, 24.62, and 25.67 kg/m2; mean leptin levels of 2.66, 2.61, and 3.58 µg/L; 18.28, 16.62, and 18.22 kg of body fat; and 2.49, 2.52, and 2.88 kg of visceral fat, respectively.

In adjusted analyses, increases in these variables were significantly associated with increasing odds of high-volume BPH. The highest quartile of serum leptin and adiponectin levels were significantly associated with 3.5-fold increased odds and 68.5% decreased odds of high-volume BPH, respectively, compared with the lowest quartiles, the researchers reported in the International Neurourology Journal (2016;20:321-328).

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The likely biologic mechanism by which obesity may promote BPH seems to be insulin resistance, the investigators explained. Chronic elevation of insulin is associated with increased availability of insulin-like growth factor-1 (IGF-1). “Insulin has been suggested to stimulate tumorigenesis by inducing IGF-1 synthesis and activating insulin and IGF-1 receptors, which often are overexpressed in cancer cells,” Dr Jung and colleagues wrote. “Moreover, insulin and IGF-1 interactions with downstream signaling pathways may impact the growth of hormonally driven tumors, such as prostate cancer; they may also stimulate BPH.”

The investigators also stated that insulin may influence transcription of genes involved in sex hormone metabolism. These genes alter the androgen to estrogen ratio and circulating level of sex hormone-binding globulin, the researchers explained. “Such alterations in the testosterone to estrogen ratio in prostate tissue may contribute to BPH development.”

Chronic inflammation and oxidative stress also may explain the link between obesity and BPH, the investigators noted. “Increased BMI is associated with adipocyte hypertrophy and death, which cause excessive cytokine production and leukocyte recruitment,” Dr Jung’s team explained. “These inflammatory changes in the tissue may provide a pro-neoplastic microenvironment.”

Although the study has a number of limitations, “we believe that obesity management and prevention may be a novel target for the prevention of BPH,” the researchers stated.

The investigators cited a meta-analysis that concluded that moderate to vigorous physical activity was associated with a 25% lower risk for BPH or lower urinary tract systems.

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1. Jung JH, Ahn SV, Song JM, et al. Obesity as a risk factor for prostate enlargement: A retrospective cohort study in Korea. Int Neurourol J 2016;20:321-328.