If you have low testosterone or suspect that you do (the symptoms could be low libido, lagging energy, depression, weight gain (particularly in your midsection), and loss of lean muscle among others), you should talk to your doc about getting the full bloodwork panel done to check your test, free test, LH, thyroid functions and more. There are a lot of options available for treating low test including HRT and HCG therapies. More and more men are experiencing hypgonadal issues at an early age (35 years old seems to be the median), which can cause lowered testosterone. It could also be a thyroid issue, though, as the two display similar symptoms. Here's a good link on low test:
http://www.thefactsaboutfitness.com/research/test.htm
If you do discover that you have low test after doing the bloodwork, I'd suggest finding a good endocrinologist or urologist who has done a lot of work with men's hormomal profile manipulation and adjustment. This is something that will be outside of your family doc's expertise, more than likely. If you have questions, please feel free to PM me. This is something I've been forced to learn a lot about.
jag