Researchers have found preliminary evidence suggesting that a mans lifetime risk of prostate cancer may be linked to the amount of testosterone circulating in his body as early as puberty or even in utero, although direct evidence of this link remains to be shown.
The two possible risk factors they foundhigh free testosterone levels in adulthood and a small shoulder span in relation to body sizeappear to be unrelated to one another. However, they are both tied to hormone levels at various stages of development, said Wendy Demark-Wahnefried, associate professor of surgery at Duke and lead author of two parts of a study that produced the findings.
While doctors will not be able to predict who will get the disease based on these two factors alone, the results suggest that free hormone levels and shoulder span could be benchmarks for determining who is at greater risk for the disease, Demark-Wahnefried said.
We have to look at how hormone levels at different points in time actually determine the risk of prostate cancer, she said. It is hypothesized that hormone levels throughout liferanging from in utero to old agedrive such events as skeletal and muscle formation, fat deposition, baldness, and that these events may provide the initial stimuli and promotion for prostate cancer. By studying the tell-tale signs that hormones leave on the body, our goal was to clearly separate those men at risk for prostate cancer from those who are not.
Demark-Wahnefrieds research, funded by the National Cancer Institute and the Cancer Research Foundation of America, set out to measure the link between prostate cancer and factors such as height, weight, musculature, and baldness. The 2-year, blinded, case-controlled study compared a group of 159 men with prostate cancer to a control group of 156 men who had come to the urology clinic for prostate screenings and other concerns such as kidney stones. Subjects ranged in age from 50 to 70 years.
In the first phase of the study, Demark-Wahnefried and her colleagues at the Duke Comprehensive Cancer Center found nearly a two-fold increase in the risk of prostate cancer among men with high free testosterone levels. While the link between testosterone and prostate cancer has been made before, previous studies have measured total testosterone.
The researchers also found a link between high testosterone levels and vertex baldness. However, baldness was not linked to prostate cancer in the study subjects, probably because baldness is as much related to age as it is to other factors such as testosterone, she said. The part of the study that looked at baldness, testosterone levels, and prostate cancer was published in the September/October 1997 issue of the Journal of Andrology.
Next Phase of the Study
In the next phase of the study, published in the September 1997 issue of the Journal of Nutrition and Cancer, researchers found that men with prostate cancer were more likely to have a narrower shoulder span in proportion to their overall body size, a trait that earlier studies have shown to be determined during puberty.
Demark-Wahnefried said those earlier studies, although quite limited in their sample size, showed that men who go through puberty later have a broader shoulder span than men who go through puberty early. She said this finding suggests that hormone levels have a direct influence on shoulder span.
While the difference in shoulder span was less than a centimeter, Demark-Wahnefried said it was the only physical factor she studied that was significantly associated with prostate cancer.
Shoulder span may provide us with a benchmark of past hormonal and/or nutritional status and help elucidate the etiology of this disease, she said.
While researchers have long believed that prostate cancer is linked to male hormone levels, Demark-Wahnefried said the existing research has yielded conflicting results, similar to the controversy surrounding estrogen as a risk factor for breast cancer.
The current studies provide strong evidence that risk of prostate cancer is, in fact, influenced by hormonal events that occur much earlier in life, such as the formation of skeletal frame, she said. However, Demark-Wahnefried said these events may originate in utero and continue to manifest themselves at developmental milestones throughout a mans life.