Purpose: We investigated whether the association between vasectomy and prostate cancer has a hormonal basis.
Materials and methods: We examined serum testosterone, dihydrotestosterone, luteinizing hormone and follicle-stimulating hormone levels by radioimmunoassay on 91 pairs of men who did and did not undergo vasectomy.
Results: Men who underwent vasectomy 10 to 19 years previously had higher dihydrotestosterone levels than age matched controls. In men who underwent vasectomy 20 years or more ago testosterone was higher than in corresponding controls. No statistically significant difference in luteinizing hormone and follicle-stimulating hormone levels was noted between the men who had had vasectomy and controls.
Conclusions: Our results indirectly support the hypothesis that there is an elevated risk of prostate cancer among men who underwent vasectomy 20 or more years previously.
PIP: Researchers compared data on 91 men who had undergone vasectomy at least 10 years earlier with data on 91 healthy men matched for age, weight, height, and neighborhood who had not undergone vasectomy to examine whether the link between vasectomy and prostate cancer is based on changes in serum hormone levels. All the men lived in suburban Xiangtan in Hunan Province, China. Cases had a higher mean serum dihydrotestosterone level than controls (1.18 vs. 1.05 nmol/l; p 0.05). Yet men who had undergone vasectomy less than 20 years earlier not only had a higher dihydrotestosterone level than age-matched controls (1.46 vs. 1.22 nmol/l; p 0.01) but had a lower testosterone/dihydrotestosterone ratio (14.5 vs. 20.1; p 0.005). On the other hand, men who had undergone vasectomy more than 20 years earlier had a higher testosterone level than age-matched controls (27.2 vs. 23.9 nmol/l; p 0.05). Men who had undergone vasectomy when they were less than 35 years old had a higher FSH level and those who were 35-39 years old at vasectomy had a higher dihydrotestosterone level than age-matched controls (19.5 vs. 14.8 mIU/ml and 1.31 vs. 1.09 nmol/l) (p 0.05). Even though men who were at least 40 years old at vasectomy had a higher dihydrotestosterone level than matching controls (1.24 vs. 1.09 nmol/l), the difference was not statistically significant. These findings suggest that vasectomy may cause a reduction in testosterone levels by minimizing the conversion from testosterone to dihydrotestosterone in the long term. Thus, they support the hypothesis that a long-term effect of vasectomy may be an elevated risk of prostate cancer. More research is needed to confirm or refute this hypothesis.