Calcium Homestasis

Calcium is the most abundant mineral and constitutes 2 % of the body mass. It is involved in muscle contraction/relaxation, blood clotting, nerve function, regulation of blood pressure, cell signaling and in bone and teeth mineralization.

P. Devi, MSc (*) • P.R. Palanivelu, MS, DNB, DNB (SGE), FALS, FMAS Bariatric Division, Upper Gastrointestinal Surgery and Minimal Access Surgery Unit, GEM Hospital and Research Centre, Coimbatore, India e-mail: This email address is being protected from spam bots, you need Javascript enabled to view it ; This email address is being protected from spam bots, you need Javascript enabled to view it

© Springer Nature Singapore Pte Ltd. 2017

P.R. Palanivelu et al. (eds.), Bariatric Surgical Practice Guide,

DOI 10.1007/978-981-10-2705-5_35

The main site of absorption of calcium is the duodenum. Calcium from diets is absorbed by the intestine through two pathways: transcellular absorption and para- cellular transport of calcium. In the duodenum, transcellular absorption is responsible for 80 % calcium uptake in low-calcium diets and less than 10 % calcium uptake in high-calcium diets and the rest will be by paracellular transport [9].

Vitamin D is important for calcium homeostasis as it regulates the calcium absorption in the small intestine [10, 11]. Vitamin D regulates calcium metabolism, insulin action, immune function and cell proliferation [12]. Magnesium is also needed for calcium absorption and to retain calcium by suppressing parathyroid hormone and by stimulating calcitonin. But excess calcium can prevent magnesium from being absorbed. Hence calcium intake should be supplemented with adequate magnesium to prevent both calcium malabsorption and magnesium deficiency, as magnesium is not stored well.

Parathyroid hormone (PTH) secretion (secreted by parathyroid glands) is controlled by calcium concentration and it has biological effects on the bones, kidneys and intestinal mucosa [13, 14]. A decrease in ionized calcium stimulates the release of PTH, which maintains calcium homeostasis by (1) increasing bone mineral dissolution, thus releasing calcium and phosphorus, (2) increasing renal reabsorption of calcium and excretion of phosphorus, and (3) enhancing the gastrointestinal absorption of both calcium and phosphorus indirectly through its effects on the synthesis of 1,25(OH)2D (calcitriol) in the body [13].

 
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