Brian Fung highlights new research suggesting "there's little basis to assume a causal relationship between age and hormone decline":
The study subjects were tested for blood testosterone at the beginning and at the end of a five-year study period. The passage of time evidently had very little effect on the sample population in the aggregate; on average, testosterone levels declined about one percent per year. But when the researchers examined test subjects in groups, they found greater declines among those who, at either end of the study, had been obese, depressed, or had quit smoking. What this suggests is that the aging process may have only a marginal role to play in the testosterone decline observed in older men.
But testosterone does decline as you get older, for whatever reason. HIV and its medications have wiped out my own testosterone production. I'm now on implants – which sure beats the fortnightly jab in the hip.