After these adjustments were made, blacks had a 15% higher testosterone level and a 13% higher free testosterone level. A 15% difference in circulating testosterone levels could readily explain a twofold difference in prostate cancer risk.

Study from 1986. Study from 2007. The study from 2007 is more relevant as it's newer and would factor in more current genetic knowledge.

For the first study I would like to know the sample size, whether or not it was randomized properly, and most importantly how do they define "black". It could very well be that some people who happened to be labeled black have the genetics to make them more vulnerable to prostate cancer than another group of people who happened to be labeled white, but it doesn't show me anything about what black is or what genes exactly are responsible for the higher testosterone levels if it's even genetics.

The 2007 study is much better. They isolate out non-hispanic white and non-hispanic black. I'm not sure why they do this but maybe they want to focus on specifically American blacks. They also included Mexican American which is good for the study as well.

After applying sampling weights and adjusting for age, percent body fat, alcohol, smoking, and activity, testosterone concentrations were not different between non-Hispanic blacks (n = 363; geometric mean, 5.29 ng/ml) and non-Hispanic whites (n = 674; 5.11 ng/ml; P > 0.05) but were higher in Mexican-Americans (n = 376; 5.48 ng/ml; P < 0.05).

So according to this result it appears testosterone levels are higher in Mexican Americans but are not significantly different between non hispanic white and non hispanic black.

Contrary to the postulated racial difference, testosterone concentrations did not differ notably between black and white men. However, blacks had higher estradiol levels. Mexican-Americans had higher testosterone than whites but similar estradiol and SHBG concentrations.

So appears there is no racial difference in testosterone according to that study. And that study was more recent and better designed than the older study with a larger sample size. This in my opinion does not indicate a racial difference between black and white. They did find slightly different hormone levels of estradiol but I doubt it has anything to do with being black or white, so I would have to see some evidence showing the cause before I form an opinion.