Height
It may have to do with male hormones. Prostate cancer is a hormone dependent cancer, which means that it depends on male hormones, primarily testosterone, to develop. Men who are hormone deficient, either as a result of disease, treatment, or castration (e.g., testicular cancer, trauma, or sexual reassignment) do not develop prostate cancer. And those who are exposed to higher levels over the course of their lifetimes are thought to be at greater risk. Tallness and childhood obesity may reflect higher testosterone levels at younger ages and thus lead to greater cumulative exposure.
The relationship between tallness and increased risk of prostate cancer has not been consistently found, but the two largest and best prospective studies of men's health in the U.S. have both confirmed the relationship. The Health Professionals Follow-Up Study, which is following nearly 50,000 men in various health-related occupations, has shown that men who are 6'2" or taller have 1.68 times the risk of developing advanced prostate cancer and over twice the risk of metastatic cancer compared to men 5'8" or shorter. The second study, the Physician's Health Study, is a randomized study of 22,000 physicians looking at the effect of beta carotene and aspirin in the prevention of cancer and heart disease. It also has shown that tallness is associated with increased risk of prostate cancer, especially at heights greater than 6'.
