1,25-Dihydroxy vitamin D2 is a potent agonist of the vitamin D receptor. Paricalcitol is a synthetic 1,25-dihydroxy vitamin D2 analog. As vitamin D deficiency, associated with chronic kidney disease, leads to an increase in parathyroid hormone (secondary hyperparathyroidism), paricalcitol is used in renal patients to block parathyroid hormone overproduction. Vitamin D deficiency is also a risk factor in cancer, cardiovascular disease, hypertension, and diabetes, and paricalcitol may have applications in those contexts as well.
