I appreciate the response. The information I found on the internet treats it as just the some total of common hormone changes that occur with age but I find that to be lacking.

In my case, I have an odd story.

Up until about 4 years ago, I found it absolutely impossible to quit smoking. For 30 years I tried to quit over and over, used patches, gum, lozenges, Zaiban, sunflower seeds, everything to quit and I couldn't last even a day with no smokes most of the time and I certainly never lasted more than a few days. Then something just switched off in me and I no longer had the addiction. I don't know why it happened, but I am more or less forced to assume it was due to some fundamental physiological change because at the time, I was in a really bad place mentally, a time when most people find the stress too much to be able to drop a crutch like smoking cigarettes.