Effects of active metabolites of vitamin D (D), parathyroid hormone (PTH), calcitonin (CT), and fibroblast growth factor 23 (FGF23) on calcium and phosphorus homeostasis. Active metabolites of vitamin D increase absorption of calcium from both gut and bone, whereas PTH increases reabsorption from bone. Vitamin D metabolites and PTH both reduce urinary excretion of calcium. In animals with vitamin D deficiency, active metabolites of vitamin D produce a net increase in bone mineralization by increasing the availability of serum calcium and phosphate. (Reproduced, with permission, from Katzung BG, editor: Basic & Clinical Pharmacology, 12th ed. McGraw-Hill, 2012: Fig. 42–1.) Source: Drugs That Affect Bone Mineral Homeostasis, Katzung & Trevor's Pharmacology: Examination & Board Review, 11e Citation: Trevor AJ, Katzung BG, Kruidering-Hall M. Katzung & Trevor's Pharmacology: Examination & Board Review, 11e; 2015 Available at: http://accesspharmacy.mhmedical.com/DownloadImage.aspx?image=/data/books/1568/tre_ch42_f001.png&sec=95703816&BookID=1568&ChapterSecID=95703813&imagename= Accessed: November 10, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved