Hypercalcemia due to endogenous overproduction of 1,25-dihydroxyvitamin D
in Crohn's disease.
Boshuis et al., "Ectopic production of 1,25-dihydroxyvitamin D
by B-cell lymphoma as a cause of hypercalcemia," Cancer, vol.
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.
Both D3 and D2 precursors are hydroxylated in the liver and kidneys to form 25-hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D
(1,25(OH)2D), the biologically active form that is tightly controlled by the body.
The authors found that the results were similar whether they measured 25-hydroxyvitamin D or 1,25-dihydroxyvitamin D
This substance is ultimately converted into the active form of vitamin D called 1,25-dihydroxyvitamin D
(calcitriol) in the liver.
(Only blood levels of 25-hydroxyvitamin D, not 1,25-dihydroxyvitamin D
, were linked to the risk of polyps.) However, above-average levels of vitamin D didn't reduce the risk of polyps in people who took the placebo.
The role of 1,25-dihydroxyvitamin D
in the mechanism of acquired vitamin D deficiency.
Vitamin D, in its active form (1,25-dihydroxyvitamin D
), is a hormone that binds to receptors in the body's cells.
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.
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).
This study aimed to determine whether endogenous 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D
levels are related to all-cause and cardiovascular mortality.