Here is a link for the temps question. It is KSman discussing his thyroid. Temps can help indicate thyroid function.
Regarding the question you asked about pititary problems, I think a whole slew of things can cause them. In my particular case I think it was extreme stress for several months due to a family situation, averaging 4 hours sleep, poor diet, no exercize etc. I also know I have a weak thyroid and that may have contributed.
Clomid or other SERMS are used to try to correct a pituitary problem. They essentially re-start it (if successful). It prompts the production of LH/FSH so that your body can produce t on its own.
I started on test injections when I realized I had low T. About a year later I am figuring out the cause and that I should have first tried to correct the problem at the source.
For people with primary hypogonadism, this isnt an option. Their problem is in the testicles so trying to fix LH etc wont help.
Because it sounds like you are secondary, Clomid might be worth looking into. - Except people on here suggest Nolvadex rather than Clomid. It has fewer side effects.