The second hydroxylation occurs in the kidneys via the enzyme 1-alpha-hydroxylase, yielding 1,25- dihydroxycholecalciferol (calcitriol), the biologically active form of vitamin D. 1,25-dihydroxycholecalciferol has a half-life of 15 hours, while 25-hydroxycholecalciferol has a half-life of 15 days. The initial hydroxylation occurs in the liver via the enzyme 25-hydroxylase and results in 25-hydroxycholecalciferol, which is used to assess the body’s reserve of vitamin D because it has a longer half-life compared to 1,25-dihydroxycholecalciferol.

Ĭholecalciferol undergoes two hydroxylation processes to activate it. Light energy is absorbed in the skin via 7-dehydrocholesterol, where the ultraviolet B (UVB) converts 7-dehydrocholesterol to cholecalciferol, an inactive vitamin D molecule. Ĭholecalciferol gets generated in the skin upon sun exposure. Īside from its known role in bone mineral metabolism, various studies have found a link between cholecalciferol supplementation and favorable prognoses of different diseases such as hypertension, type 1 and 2 diabetes, cardiovascular disease, cancer, rheumatoid arthritis (RA), polycystic ovarian syndrome (POS), multiple sclerosis (MS), systemic lupus erythematosus (SLE), and various dermatologic diseases. The off-label indications for cholecalciferol include hypothyroidism, prevention of osteoporosis, and Vitamin D insufficiency/ deficiency in both healthy patients or those with chronic kidney disease (CKD). The labeled indication for cholecalciferol is dietary supplementation. During winter and in areas with minimal sun exposure, dietary supplementation is necessary for optimal musculoskeletal health. Its primary function is to maintain normal calcium and phosphate levels in the serum.

Cholecalciferol, also known as vitamin D3, is a secosteroid produced by the skin and can also be present in certain foods such as dairy products, eggs, and fish.

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