In serum, most of the calcium ion is bound to albumin. Less than 50% of calcium is in the ionised form in serum, the rest being bound to protein and other anions like phosphate, citrate etc. The ionised form is most important in regulation of body functions. Intestinal absorption of calcium is activated by 1,25 (OH) 2 D3. Most of the calcium that is filtered by the kidneys is reabsorbed throughout the nephron, around 55% in the proximal convoluted tubule. Calcitonin is the most important factor regulating calcium excretion. Secreted by the parafollicular cells of the thyroid gland, this hormone responds to raised calcium levels by inhibiting bone resorption and increasing renal excretion. Increased intestinal absorption is the main cause for raised calcium levels in sarcoidosis due to increased production of 1,25 OH vitamin D from activated pulmonary macrophages.
Posted on: Fri, 21 Mar 2014 20:10:42 +0000
Trending Topics
Recently Viewed Topics
© 2015