1alpha-hydroxy-3-epi-vitamin d3

**1alpha-hydroxy-3-epi-vitamin d3** is a synthetic analog and natural metabolite of 1alpha,25-dihydroxyvitamin D3. It acts as a potent suppressor of parathyroid hormone (PTH) secretion with minimal calcemic effect[2][4][5]. Its biological activity is mediated through binding to the vitamin D nuclear receptor (VDR), functioning as an agonist and inducing tissue-specific transcriptional responses—including antiproliferative and differentiation effects in keratinocytes and parathyroid cells[3]. The compound displays higher selectivity for PTH suppression relative to the risk of hypercalcemia, making it promising for treating secondary hyperparathyroidism in chronic renal failure[5]. Its mechanism involves VDR activation, but unlike 1alpha,25-dihydroxyvitamin D3 (calcitriol), it causes significantly less elevation of serum calcium[5]. It is structurally characterized by epimerization at the C3 position. The molecule can be synthesized and has shown in vivo metabolic stability and biological activity in several cell and animal models[3][5].

Other names

(1S,3S,5Z)-5-[(2E)-2-[(1R,3aS,7aR)-7a-methyl-1-[(2R)-6-methylheptan-2-yl]-2,3,3a,5,6,7-hexahydro-1H-inden-4-ylidene]ethylidene]-4-methylidenecyclohexane-1,3-diol(5Z,7E)-(1S,3S)-9,10-seco-5,7,10(19)-cholestatriene-1,3-diol1alpha-hydroxy-3-epivitamin D31alpha-hydroxy-3-epicholecalciferol