I will also add my wife has been diagnosed with an under active thyroid. She has researched it to the depths, and knows more than the GP, which is easy.
She managed after a big battle to get prescribed a mix of t3 and t4, where just t4. Is usually prescribed, as t3 is expensive. It works, and she insisted she went to see the regional specialist in thyroid who said this meds seem the best for her, and he recommended staying on it. S it was an up yours to the GP.
Our GP is nice, but she hates me and the missus going in, as she knows her stuff, and so do I. I never go in for general health stuff, but have been regular with my shoulder, being fit they dismiss you, but eventually I got it sorted. Next was my balls after the snip. There was no way I should be in the pain I was being fit..ohh it can take weeks... I said, hang on its usually a couple of weeks not a couple of months...
It sometimes don't work being a working healthy fit person. You really have to get down to it sometimes.