Biochemistry 3386B Study Guide - Osteoporosis, Malabsorption, Calcification
10 Jul 2014
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Document Summary
Production is controlled by ca, p04 and pth . hypercalcemia and hyperphosphatemia reduces production by inhibiting 1 hydroxylase. 1,25(oh)d also regulates its own concentration by negative feedback. Pth and hypophosphatemia stimulate hydroxylation of vitamin d through 1 hydroxylaze. Physiological activity steroid hormone, travels through membranes to nuclear receptor. In bone it stimulates minerlization, in kidney it stimulates ca and p04 resorption, and in intestine it stimulates ca and p04 absorption. Sources sunlight exposure . 90% in blood . season aging sunscreen and skin pigmentation all affect absorption . found in salmon tuna liver eggs and milk. Deficiency caused by minimal sun exposure, nutritional deficiency, malabsorption (intestinal problem), kidney disease (less alpha 1 hydroxylation) and liver disease (less 25 hydroxylation) inherited conditions. Clinical features seen in elderly, breast feeding, darker skin poigmentation, vegitarians (strict). Common fracture, bone weakness and poor calcification, growth abnormalities, rickets, general muscle weakness, poor bone mineralization = tetany, osteopenia.
