[Bone and bone related biochemical examinations. Hormone and hormone related substances. Vitamin D (25D, 1,25D); measurements and clinical significances].

Vitamin D plays an important role in regulation of calcium homeostasis and bone metabolism. Among vitamin D metabolites, 25-hydroxyvitamin D (25-OH-D) can be used for the evaluation of vitamin D nutritional status. In contrast, 1,25-dihydroxyvitamin D (1,25 [OH] 2D) can be used for the diagnosis of hyperparathyroidism, renal malfunctions, and other calcium metabolism-related diseases. Serum 25-OH-D concentration can be measured with radioimmunoassay (RIA), enzyme immunoassay (EIA), enzyme-linked immunosorbent assay (ELISA), chemiluminescence protein-binding assay (CLPBA), high performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry/mass spectrometry (LC-MS) methods. Likewise, serum 1,25 (OH) 2D can be measured with RIA, EIA, radioreceptorassay (RRA) and ELISA methods. Clinicians are required to recognize the characteristics of each method and use serum concentrations of 25-OH-D and 1,25 (OH) 2D as biochemical markers for the diagnosis of bone diseases.