TRC: Vitamin D analogues

Vitamin D analogues

Vitamin D and its analogues play an important role in the control of calcium blood levels. Vitamin D is taken up in the intestine and transported to the liver. The liver converts vitamin D into 25 (OH)D3. For the diagnosis of vitamin D deficiency the concentration of 25(OH)D3 in plasma is measured. This metabolite is converted by the kidney into the active 1,25(OH)2vitamin D3. This metabolite also stimulates calcium resorption in the kidney.

The vitamin D analogues (such as cholecalciferol) have a cholesterol-like chemical structure like steroids and their action on cells occurs similarly compared to steroids. After binding to its nuclear receptor, the hormone receptor complex alters transcription of target genes. In case of hypoparathyroidism, calcitriol and alfacalcidol are preferred as treatment. The initial dose is 0,25 μg daily orally in case of hypoparathyroidism. The maintenance dosage should be carefully set after serum calcium measurements.

See also therapy with vitamin D analogues in the nephrology chapter.

I. 25-OH vitamin D3 is the active form of vitamin D3.

II. Only a combination of vitamin D and calcium supplements can regulate blood calcium levels satisfactorily.

Extra info: 1,25 (OH)2vitamin D3 is the active form of vitamin D present in the body. In case of hypoparathyroidism only suppletion of both calcium and vitamin D is effective (PTH is not available for treatment).

Option explanation:

I is true, II is false

I is true, II is true

I is false, II is false

I is false, II is true

Vitamin D analogues

Vitamin D analogues

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