According to the research by Patrick Woods and others from Spain and Mexico (and I think somewhere else) there's a lot of evidence that fibro is a form of hyperadrenergic POTS. This means the HPO axis doesn't work properly so we have bizarre flight and fight responses to such dangerous things as standing up. Because of the adrenal effects we have difficulty making dopamine from Norepinephrine (noradrenaline) and then we might have problems with dopamine uptake or reuptake. It also effects catacholomenes. It's all complicated but the upshot is we get either POTS or like me IST (which many researchers think is a form of POTS) and other stuff like pain and tremor. My tremor is awful now. There was a very small scale study with 12 (I think it was 12) women with FMS taking Ldopa which showed some promise but there's been no follow up that I'm aware of. I've decided not to get the complicated tests done because a) there's no treatment and b) I don't believe there's enough experienced people in the NHS who can do these tests properly. It's also been considered that as the Pituitary runs the hormone show overall his might explain why so many more women than men get FMS.