7. VITAMIN D SYNTHESIS SKIN LIVER KIDNEY 7- DEHYDROCHOLESTEROL VITAMIN D 3 VITAMIN D 3 25(OH)VITAMIN D h 25-HYDROXYLASE 25(OH)VITAMIN D 1,25(OH) 2 VITAMIN D ( ACTIVE METABOLITE ) 1 -HYDROXYLASE TISSUE-SPECIFIC VITAMIN D RESPONSES
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12. CALCIUM, PTH, AND VITAMIN D FEEDBACK LOOPS NORMAL BLOOD Ca RISING BLOOD Ca FALLING BLOOD Ca SUPPRESS PTH STIMULATE PTH BONE RESORPTION URINARY LOSS 1,25(OH) 2 D PRODUCTION BONE RESORPTION URINARY LOSS 1,25(OH) 2 D PRODUCTION
Dehydration decreases renal calcium excretion and patients take in less fluids b/c of n/v. HYPERCALCEMIC CRISIS –; severe hypercalcemia- high ca 13-15, volume depletion, and altered mental status.