1,25-(OH)2 Vitamin D ELISA Kit

Sample

Serum and plasma

Species Reactivity

Human

Detection Method

Competitive-ELISA

Intended Use

This ELISA is intended for the quantitative determination of 1,25-dihydroxyvitamin D in serum and plasma. For research use only.

Contents of Kit

No.	Components	Size	Storage Conditions
1	Pre-coated microtiter plate	12 × 8 wells	2-8 °C
2	Wash buffer concentrate (10×)	1 × 100 ml	2-8 °C
3	Ethanol	1 × 1.5 ml	2-8 °C
4	Tris-HCl buffer	1 × 30 ml	2-8 °C
5	Detection antibody	1 × 25 ml	2-8 °C
6	Standards	6 × 2.5 ml	2-8 °C
7	Control A	1 × 2.5 ml	2-8 °C
8	Control B	1 × 2.5 ml	2-8 °C
9	Conjugate	1 × 24 ml	2-8 °C
10	Substrate	2 × 15 ml	2-8 °C
11	Stop solution	1 × 15 ml	2-8 °C
12	Foil	2 × 1

Storage

Store whole kit at 2-8 °C until expiration date.

Precision

Intra-Assay (n = 20)

Inter-Assay (n = 20)

Sensitivity

The sensitivity was set as B₀ - 2SD. The zero-standard was measured 20 times.

General Description

Vitamin D is either produced in the skin (under the influence of UV light) or taken up from nourishment. The storage type of vitamin D, namely 25-hydroxyvitamin D, is formed in the liver. The hormone 1,25-dihydroxyvitamin D (D hormone) is formed in a second hydroxylation step in the kidney. The responsible enzyme, the kidney 1α-hydroxylase, is subjected to a rigid control through hormones (especially parathyroid hormone) and its activity is influenced by the serum concentrations of calcium and phosphate.
The serum concentration of 1,25-dihydroxyvitamin D normally re-adjusts itself to the demands of metabolism. Deviations from the normal range of 1,25-dihydroxyvitamin D must therefore always be interpreted in the context of the remaining parameters of the calcium metabolism. The serum concentration of 1,25-dihydroxyvitamin D decreases only in seldom cases of vitamin D deficiency. For the diagnosis of vitamin D deficiency, the precursor metabolite, 25-hydroxyvitamin D, should be measured.
The reason for a non-physiological deficiency of 1,25-dihydroxyvitamin D can be found in metabolic disturbances, caused either by genetic defects of the enzyme 1α-hydroxylase (rare) or kidney malfunctions (more common). Even a slightly impaired kidney function can lead to a decrease of the 1,25-dihydroxyvitamin D concentration.
Since 1,25-dihydroxyvitamin D has important functions in calcium metabolism as well as supplementing secretion of parathyroid hormone from the parathyroid glands, increasing kidney malfunctioning leads to development of renal osteopathy, which is characterized by osteomalacia and osteitis fibrosa.
Treatment of renal osteopathy consists of the administration of 1,25-dihydroxyvitamin D (calcitriol) or the prohormone 1α-hydroxyvitamin D. In renal tubules, malfunctions decreased or relatively low levels of 1,25-dihydroxyvitamin D (e. g. diabetes insipidus, Fanconi syndrome) are found. A non-physiological over-production of 1,25-dihydroxyvitamin D arises in granulomatosis (e. g. sarcoidosis), where extrarenal synthesis of 1,25-dihydroxyvitamin D occurs. This can lead to hypercalcaemia. Also in idiopathic hypercalciuria, a relatively high level of 1,25-dihydroxyvitamin D is found. Increased concentrations of 1,25-dihydroxyvitamin D can be seen in case of non-functional vitamin D receptors (rare), during calcium deficient nutrition, as well as a result from overproduction of parathyroid hormone (primary hyperthyroidism).