Great name first and welcome to the Mayo Crew of Seakers of knowledge for their own health control! In my humble opinion this is an endocrinology issue. Have they ran cortisol and an ACTH test on you (also monitoring insulin uptake and sugar and aldosterone)? The reason for this test is for adrenal insufficiency or precursor to Addison’s disease, which is my issue. Please look up all of the possible symptoms and see if you don’t fit the bill. Lethargy is the key component, but I had 31 symptoms and all fit about five autoimmune or other. There is primary and secondary. Primary is your adrenal gland , which they will probably want an MRIof. The secondary is the pituitary gland sending the hormone that tell the adrenal gland to secret the cortisol. Without cortisol you have no fuel because it combines with your cholesterol to make your energy. If it is secondary and your pituitary gland is messed up then you will have out of whack T3 T4 and TSH along with low testosterone. See where I am going with this? They should also get an MRI of your pituitary gland. Brace, because it is manageable but with continuous doses (daily x2) of either hydrocortisone or prednisone- normally the latter, but there is no cure and it is progressive and the prednisone has a whole heap of side effects. Look it up before agreeing to it. What you are most likely experiencing when you “crash” and can’t control your body temp is referred to as an adrenal storm or crisis. This is seriously a dangerous situation and you should try and avoid ANY stress at all. Easier said than done, but your life depends on it. Since I do not know your personality or your stress load, it is difficult for me to discern how often you will experience this, but this is also your fight or flight mechanism. Like going to the well for energy to “deal” and the well is dry. Read read read and take some control of this yourself. I saw 13 doctors prior to my last visit to Mayo. All were baffled, but if you have thyroid function problems and hot flashes (uncontrollable body temp) and unbelievable fatigue, then I would take the above advice. Tell your endo what tests you want and why. Do NOT TAKE NO FOR AN ANSWER! Best of luck to you and keep us posted. Oh yes, this is 70% of the time due to an underlying autoimmune, but there are about a billion. Treat the symptoms first and get in better control and then go after the autoimmune as you can. Much love and may God provide you the strength and the doctors the wisdom to help you! Best wishes, Sean L. Roop – BIGGEST MAYO FAN ON THE PLANET!