BIO 12 Lecture Notes - Lecture 30: Vitamin D Deficiency, Bone Resorption, Cholecalciferol
Document Summary
Stimulates synthesis of calcitriol, which leads to increased absorption of calcium in digestive tract from foods. Synthesized form vitamin d3 (dietary intake, fish, milk, sunlight exposure) Stimulated by pth and low plasma calcium concentration. Targets digestive tract and kidneys: digestive increases calcium absorption, kidney increases calcium reabsorption so that calcium isn"t lost through urine. May be caused by lack of sunlight, lack of adequate absorption in the small intestine (celiac), kidney or liver problems (processing of vitamin d) Extreme vitamin d deficiency: rickets and osteocalcin. Secreted from c cells of the thyroid gland. Decreased bone mass leading to bone fragility and increased fracture risk. Can be seen through a bone density test: x-ray to measure how many grams of calcium is in bone. Risk factors: aging (balance of resorption/deposition, menopause (lack of estrogen, genetic predisposition, lack of physical activity, obesity, cigarette smoking, excessive alcohol consumtion.
