A male has normal testosterone levels but low lh \fsh levels. what are the chances that the low lh/fsh are the cause of a low libido? and why?

Doesn'tworkthatway!: 1st, there are many factors related to libido, not just testosterone (check out my other posts here on that topic) eg job, money, partner, family etc. 2nd, there's a wide range of normal, like passing grades from d- up to a+. 3rd, lh & fsh are brain signals to testes to produce t, so really unrelated to libido. Low lh & fsh either from outside source of t or pituitary mass (but this causes low t).

Mass Spec: Make sure they are running your testosterone tests with a mass spectrometer. It is a very specific test. Most labs dont run that as a routine, so you need to ask specifically for it.