Vitamin D: Metabolism and Function

ISBN-13: 9783642813085 / Angielski / Miękka / 2011 / 80 str.

H. F. DeLuca

Opis

Because diseases of the bone are often less acute and less lifethreatening than dis eases of the circulatory system, gastrointestinal tract, kidney, liver, and the nervous system, they have received a disproportionately smaller amount of attention in the medical world. With the average increasing life span of man as a result of improve ments in modern medicine, espe ially in the pediatric field, the seriousness of many metabolic bone diseases has indeed become more obvious. In addition, other improvements in medicine, such as hemodialysis for the preservation of renal failure patients, have permitted the development of other consequences of diseased kidneys, one of which is the appearance of renal osteodystrophy. Finally, the appearance of several genetic disorders in the area of metabolic bone disease has been underscored by the solution of other pediatric diseas s of much more serious consequences. These emerging problems all suggest that much remains to be learned concerning the sys temic control of bone, both as a structural organ and as a reservoir for the important elements of calcium and phosphorus so essential for the support of life in complex multicellular organisms of which man is the most important. As will be demonstrated in the historical portion of this manuscript, the existence of the three most important humoral factors regulating bone metabolism and func tion are now known."

Spis treści

A. Introduction.- B. Historical Aspects.- C. The D Vitamins and Their Precursors.- D. Metabolism of Vitamin D.- I. Absorption of Vitamin D3.- II. Production of Vitamin D in the Skin.- III. Storage of Vitamin D.- IV. Role of the Liver in Production of 25-Hydroxyvitamin D3.- V. Metabolism of 25-Hydroxyvitamin D3 to 24,25-Dihydroxyvitamin D3.- VI. Production of 1,24,25-Trihydroxyvitamin D3.- VII. Other Metabolites of Vitamin D3.- VIII. Metabolism of Vitamin D2 and Dihydrotachysterols.- E. Regulation of Vitamin D Metabolism: The Kidney as an Endocrine Organ.- I. Regulation of 25-Hydroxyvitamin D3 Production.- II. Regulation of 1,25-Dihydroxyvitamin D3 Production by Calcium and Parathyroid Hormone.- III. Regulation of 1,25-Dihydroxyvitamin D3 Metabolism by Serum Phosphorus Concentration.- IV. Regulation of 25-Hydroxyvitamin D3-24-Hydroxylase by 1,25-Dihydroxyvitamin D3, Parathyroid Hormone, and Ambient Calcium Concentration.- V. Regulation of Vitamin D Metabolism by the Sex Hormones.- VI. Mechanisms of Regulation of the Renal Hydroxylases.- VII. Calcium Homeostatic Mechanisms Involving the Vitamin D Endocrine System.- F. Functions of Vitamin D.- I. Intestine.- 1. Calcium Transport.- 2. Factors which Regulate Intestinal Calcium Transport by Regulating Vitamin D Conversion to l,25-(OH)2D3.- 3. The Molecular Mechanism of Action of l,25-(OH)2D3 in Intestinal Calcium Transport.- 4. Intestinal Phosphate Transport.- 5. Stimulation of Intestinal Calcium Transport by Phosphate Deprivation.- II. Functions of Vitamin D in Bone.- 1. Mineralization.- 2. Bone Calcium Mobilization.- 3. Other Possible Roles of Vitamin D in Bone.- III. Kidney.- IV. The Function of Vitamin D in Muscle and Elsewhere.- G. Analogs of 1,25-Dihydroxyvitamin D3 and 25-Hydroxyvitamin D3.- I. Analogs of 25-Hydroxyvitamin D3.- II. l?-Hydroxyvitamin D3 and l?-Hydroxyvitamin D2.- III. 3-Deoxy-l?-Hydroxyvitamin D3 and 3-Deoxy-l,25-Dihydroxyvitamin D3.- IV. Other Analogs of Vitamin D.- H. Use of Vitamin D Compounds in Medicine, Especially 1,25-Dihydroxyvitamin D3.- J. Summary and Conclusions.- References.