New aspects of vitamin D metabolism and action - addressing the skin as source and target.

Nat Rev Endocrinol. 2020 Feb 6. doi: 10.1038/s41574-019-0312-5. [Epub ahead of print]
New aspects of vitamin D metabolism and action - addressing the skin as source and target.
Bikle D1,2, Christakos S3.

Vitamin D has a key role in stimulating calcium absorption from the gut and promoting skeletal health, as well as many other important physiological functions. Vitamin D is produced in the skin. It is subsequently metabolized to its hormonally active form, 1,25-dihydroxyvitamin D (1,25(OH)2D), by the 1-hydroxylase and catabolized by the 24-hydroxylase. In this Review, we pay special attention to the effect of mutations in these enzymes and their clinical manifestations. We then discuss the role of vitamin D binding protein in transporting vitamin D and its metabolites from their source to their targets, the free hormone hypothesis for cell entry and HSP70 for intracellular transport. This is followed by discussion of the vitamin D receptor (VDR) that mediates the cellular actions of 1,25(OH)2D. Cell-specific recruitment of co-regulatory complexes by liganded VDR leads to changes in gene expression that result in distinct physiological actions by 1,25(OH)2D, which are disrupted by mutations in the VDR. We then discuss the epidermis and hair follicle, to provide a non-skeletal example of a tissue that expresses VDR that not only makes vitamin D but also can metabolize it to its hormonally active form. This enables vitamin D to regulate epidermal differentiation and hair follicle cycling and, in so doing, to promote barrier function, wound healing and hair growth, while limiting cancer development.

Vitamin D really is special. What do you think of vitamin D lamps (example of one)? I have a feeling they could help sprout hair, especially in the winter days.

Biffy wrote:Vitamin D really is special. What do you think of vitamin D lamps (example of one)? I have a feeling they could help sprout hair, especially in the winter days.

Yes, I would say probably a very good idea.

Is it true that showering removes vitamin D from the skin? I can't seem to find anything convincing one way or the other. Some say it's soap only that removes the vitamin D.

I find that if I don't rinse my face and hair every day thoroughly in very cold water things will look ugly...

Rudiger wrote:Is it true that showering removes vitamin D from the skin? I can't seem to find anything convincing one way or the other. Some say it's soap only that removes the vitamin D.

I find that if I don't rinse my face and hair every day thoroughly in very cold water things will look ugly...

Fortunately, this is a myth.

Biffy wrote:Vitamin D really is special. What do you think of vitamin D lamps (example of one)? I have a feeling they could help sprout hair, especially in the winter days.

I built decks all summer one year. 8 hrs a day in shorts and a T shirt. I was about as tan as I can get, and at the end of the summer I had my vitamin D levels checked. On the scale that aims for 60-80 units, I was only about 40-50.