Agents That Affect Bone Mineral Homeostasis BY S

Agents That Affect Bone Mineral Homeostasis BY S. Bohlooli, Ph. D School of Medicine, Ardabil University of Medical Sciences

Hormonal regulators of bone mineral homestasis n n n PTH Vitamin D Calicitonin Estrogens Glucocorticoids

Bone mineral homeostasis

The hormonal interactions controlling bone mineral homeostasis

Vitamin D and its major metabolites and analogs Chemical and Generic Names Abbreviation Vitamin D 3; cholecalciferol D 3 Vitamin D 2; ergocalciferol D 2 25 -Hydroxyvitamin D 3; calcifediol 25(OH)D 3 1, 25 -Dihydroxyvitamin D 3; calcitriol 1, 25(OH)2 D 3 24, 25 -Dihydroxyvitamin D 3; secalcifediol 24, 25(OH)2 D 3 Dihydrotachysterol DHT Calcipotriene (calcipotriol) None 1 a-Hydroxyvitamin D 2; doxercalciferol 1 a(OH)D 2 19 -nor-1, 25 -Dihydroxyvitamin D 2; paricalcitol 19 -nor-

Conversion of 7 -dehydrocholesterol to vitamin D 3 and metabolism

Actions of Parathyroid Hormone (PTH), Vitamin D, and FGF 23 on Gut, Bone, and Kidney PTH Increased calcium and phosphate absorption (by increased 1, 25[OH]2 D production) Vitamin D Increased calcium and phosphate absorption by 1, 25 (OH)2 D FGF 23 Decreased calcium and phosphate absorption by decreased 1, 25(OH)2 production Kidney Decreased calcium excretion, increased phosphate excretion Calcium and phosphate excretion may be decreased by 25(OH)D and 1, 25(OH)2 D 1 Increased phosphate excretion Bone Calcium and phosphate resorption increased by high doses. Low doses may increase bone formation. Increased calcium and Decreased mineralization phosphate resorption by due to hypophosphatemia 1, 25(OH)2 D; bone formation may be increased by 1, 25(OH)2 D and 24, 25(OH)2 D Net effect on serum levels Serum calcium increased, serum phosphate decreased Serum calcium and Decreased serum phosphate both increased phosphate Intestine

Secondary Hormonal Regulators of Bone Mineral Homeostasis n n n Calcitonin Glucocorticoids Estrogens

Nonhormonal agents n n n Bisphonates Calcimimetics Thiazides Fluoride Other drugs n n n Gallium nitrate Plicamycin Strontium Ranelate

The structure of pyrophosphate

Typical changes in bone mineral density with time after the onset of menopause