The thyroid is the master of the endocrine system so anyone who has a low sex drive should have their thyroid checked. Most MDs only do a TSH test which once you understand the thyroid/pituitary relationshiop is only part of the equation. Free T3 and Free T4 should also be checked. T3 and T4 are two of the thyroid hormones produced and usually one or both will be low. I believe low thyroid is much more prevalent than most people think because of MD's only doing the TSH test.
Estrogen and Progesterone levels can also be checked.
So many questions. I will get to them all but have to do some work first. Thanks for all the ideas and thoughts.