I have been stuck at 15:00 for 5k for years. I have also noticed an extreme drop in sex drive. I told my doc this and he suggested my testosterone may be low, so he tested me and it is below 200. He says that if I want he can get it up close to 1000 which is well above average. How much faster will this make me? 14:40 would be nice! I only plan to do it if the good outweighs any possible side effects.
It will be hard for you to devise workouts that will leave you with DOMS on the second day.
Yes, no doubt, you will get faster because you will do more workouts, more cross training and more weight lifting and not be tired. The challenge will be finding enough time away from you family.
HRT can help aging men recapture some youth, but talk to your doctor about what the long term plan is for HRT. A lot of people who go on it can never ever come off of it, because you body (already producing low levels of Test) completely stops producing Test at all. If you do choose to start it, understand it is likely not something you will ever be able to stop.
I know I would much prefer normal/high Test levels than low ones, and the health risks associated with HRT are not really that crazy, but understand what you are getting yourself into. Short term running goals should absolutely not factor into the decision.
Try gaining some weight. Testosterone is synthesized from fat. If you're getting less than 20 percent of your calories from fat, and have no fat stores to compensate, then of course you'll have low testosterone. Your doctor oughtta know that.
I learned this from natural bodybuilders, who destroy all their body fat and have to be very careful managing their hormone levels as a result.
Take as much as you need. It isn't cheating, it is getting your body back to normal. Most masters runners do it.