Vitamin D acts more like a hormone than a vitamin
20 hours ago
- #Health Implications
- #Vitamin D
- #Steroid Hormone
- Vitamin D is more accurately classified as a steroid hormone rather than a vitamin, as it is synthesized by the skin under UVB sunlight and regulates numerous genes.
- Vitamin D activation involves two steps: hydroxylation in the liver to form 25-hydroxyvitamin D (measured in blood tests), and further hydroxylation in the kidney to produce calcitriol, the active hormone.
- The vitamin D receptor (VDR) belongs to the nuclear receptor superfamily, similar to receptors for estrogen, testosterone, cortisol, and thyroid hormone, regulating 1,000 to 2,000 genes across various tissues.
- Vitamin D has broad systemic effects beyond bone health, including reducing risks of repeat heart attacks, autoimmune diseases, respiratory infections, cancer mortality, falls, and progression to type 2 diabetes.
- Viewing Vitamin D as a hormone impacts testing and supplementation: optimal blood levels (30-80 ng/mL) are higher than deficiency thresholds, and overdose risks exist due to its steroid nature.
- Standard measurement of Vitamin D status is through the 25-hydroxyvitamin D blood test, with levels influenced by sunlight exposure, diet, and supplementation.