Thyroid Hormones Directly Alter Human Hair Follicle Function

Here's the link to the complete author's submission (ie: not yet vetted by the publisher) so you can read the whole article, but it's got some errors.

http://jcem.endojournals.org/cgi/rap...jc.2008-0283v1

The conclusion is that both hair pigment and hair follicle cycling, are directly affected by both T3 and T4.

So this is additional incentive to keep on looking after those thyroid hormones (as if we needed any more incentive).