The main function of 1,25-dihydroxyvitamin D
for bone mineralisation is to maintain the calcium-phosphate product in the circulation, which allows passive mineralisation of collagen bone matrix.
3] enters the circulation and is metabolized sequentially first in the liver to 25-hydroxyvitamin D [25(OH)D] and then in the kidney to 1,25-dihydroxyvitamin D
The 1,25-dihydroxyvitamin D
concentration is unreliable for making a primary diagnosis of hypovitaminosis D because it depends on the activity of 1a-hydroxylase (which converts 25-hydroxyvitamin D into the active 1,25-dihydroxyvitamin D
), which is regulated by calcium, phosphate, and parathyroid hormone (PTH).
Hypercalcemia results from increased calcium absorption secondary to 1,25-dihydroxyvitamin D
production by sarcoid granulomas.
When the highest energy ultraviolet light, called UVB, penetrates the skin, it converts a precursor into vitamin D, which becomes 25-hydroxyvitamin D in the liver, and is then activated to 1,25-dihydroxyvitamin D
in the kidneys.
Assay of circulating 1,25-dihydroxyvitamin D
involving a novel single-cartridge extraction and purification procedure.
This study aimed to determine whether endogenous 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D
levels are related to all-cause and cardiovascular mortality.
The available data show that Sr absorption is increased by therapeutic administration of 1,25-dihydroxyvitamin D
or renal activation of 25-hydroxyvitamin D-1a-hydroxylase [14, 15].
The active form of vitamin D, 1,25-dihydroxyvitamin D
, is made in many different tissues, including colon, prostate, and breast.