Somewhere in the late Oliver Sacks's archive is a ten page letter from me, (prompted by him) on what it felt like to come out of ten years of severe hypothyroidism. He was very interested in altered states - particular those not caused by narcotics - though he was interested in those too. I was interviewing him for the World Service about his very good book on migraine and mentioned that I had enjoyed an essay he wrote where a man with hypothyroidism faded away in the corner until it was diagnosed. They gave him substitute thyroxine (which is what I take), he recovered but he died soon after. By recovering it brought a cancer tumour to life.
(The essay by Sacks on hypothyroidism is called 'Cold Storage' and it was first published in Granta.)