chocmouse, I think the GPs start with the least invasive/expensive suggestions first for broad symptoms like tiredness, aches and pains, sleep disturbances, etc. I think if you had come back for another appointment and said, "Well that didn't work, what else you got?" he would have suggested blood/urine tests that would show the thyroid/vitamin deficiencies. That is what happened to me. But they don't want to spend your money on tests when you have a problem that could resolve itself for nothing. Some people think they can just take a pill and solve all problems (my husband at times) but that's not necessarily the best way to deal with symptoms.

It works the other way too; I'm taking the thyroid pills and my numbers are normal so "why are you still complaining?" is often the attitude I get if I mention sleep, tiredness, etc.