COMMENT:

True enough. But remember Reynaud's is NOT common. Cold hands are.

Iron deficiency in a woman of 30 is common (5% at least), but it
usually causes more than just cold hands--- often frank cold
intolerance is seen. And it's not likely in somebody who had the
problem even before puberty.

The average case of cold hands is NOT due to "poor circulation" in any
way that makes any pathological difference. The hands are getting good
amounts of blood, but their skin circulation is shut down to minimal,
as it would be in cold weather.  However, that condition is not
dangerous. It's mainly "cosmetic" as it results in clammy handshakes.

It can be treated with drugs if it's making a big difference in your
life (maybe you're a politician?). Antihistamines with anticholinergic
activity (benedryl, etc) may help--- but they also may make you sleepy.
Some alpha blocker drugs (Normodyne, Cardura, Hytrin) may cause enough
dilation to give you a temp change. Non-selective beta blockers
(Inderal) help some people. So does thyroid  supplementation if you're
deficient, and a slight overdose of thyroid (in nodule-suppression
range) even if you're not technically deficient.  But again, unless the
social problem is terrible, it seems not worth the risk of using a
medical/pharmacological fix.

SBH