Skin is the largest organ of the integumentary system made up of multiple layers
of ectodermal tissue.
Skin Hormones:
As ultraviolet radiation strikes the skin, it triggers the conversion of dehydrocholesterol
(a cholesterol derivative) into calciferol (vitamin D3). Calciferol travels in the
blood to the liver where it is converted into 25OH vitamin D3.
This compound travels to the kidneys where it is converted into calcitriol (1,25
OH2 vitamin D3). This final step is promoted by the parathyroid hormone (PTH)
Although called a vitamin, calciferol and its products fully qualify as hormones
because they are:
