Physiology of Vitamin D
Vitamin D is either absorbed by dietary intake or manufactured when epidermal 7-dehydrocholesterol converts UVB rays in the range of 290 nm to 310 nm hitting the skin into previtamin D3.[1,6,10,23] A thermal reaction causes previtamin D3 to convert into vitamin D3, also named cholecalciferol, within the epidermis. Vitamin D3 is transported via vitamin D binding proteins to the liver, where it metabolizes into 25(OH)D, also named calcifediol, the inert form of vitamin D. Tightly regulated by parathyroid hormone, 25(OH)D converts to 1, 25-dihydroxy-vitamin D (1,25[OH]2D), also named calcitriol, the active hormonal form of vitamin D, in the kidneys and other extra-renal tissues. 1,25(OH)2D binds to vitamin D receptors to regulate cellular function in several tissues located in the body, including brain neurons.
Obradovic et al. demonstrated a relationship between vitamin D receptors and the regulation of glucocorticoid signaling in rat models, an important finding because dysfunctional glucocorticoid signaling has been implicated in disorders such as major depressive disorder. Glucocorticoids, a type of cortisol, are increased in the presence of major depressive disorder while bone mineral density (BMD) is decreased. Decreased BMD occurs when bone formation decreases and bone reabsorption increases, which also occurs in vitamin D deficiency. While the exact mechanisms for the link between glucocorticoids, vitamin D receptors, and mood disorders have yet to be determined, evidence exists to support future research exploring these associations.
J Midwifery Womens Health. 2008;53(5):440-446. © 2008 Elsevier Science, Inc.
Cite this: Vitamin D and Mood Disorders Among Women: An Integrative Review - Medscape - Sep 01, 2008.