AdvertisementsCalcium homeostasis or metabolism refers to the controlled regulation of calcium level in the extracellular fluid within a narrow range. The extracellular fluid levels of the mineral must be maintained to achieve optimal functionality. Any increase in the levels above the regulated range may cause disorders like hypercalcemia; decrease in levels will cause hypocalcemia and osteoporosis.
Calcium is the most abundant mineral in the human body and contributes to many biochemical processes including functioning of the neuromotor systems and blood coagulation. The biological processes that contribute to its homeostasis are intestinal absorption pathways, bone remodeling processes, renal reabsorption and excretion processes and endocrine metabolism and regulation.
Total and free calcium homeostasisNearly 99% of the body's calcium is present in bones, mostly as hydroxyapatite crystals.
Bone remodeling process and homeostasisBone metabolism is a continuous process. Old bones are resorbed and new bone is formed to keep pace with the growth and repairs. Further bone is the source for maintaining calcium homeostasis in case of lowered levels in the serum. When the serum concentration of the mineral increases, to maintain the homeostasis, the mineral is actively removed from the serum by deposition on to the bones and also by excretion.
Parathyroid Hormone (PTH) in metabolismParathyroid Hormone (PTH) is the main player in bringing about the homeostasis or metabolism in the serum levels of the mineral.
The PTH secretion is controlled by negative feedback from the serum levels. PTH also stimulates production of hormonally active form of vitamin D in the kidney. PTH also decreases the excretion and increases reabsorption of this mineral by the kidneys for the mineral metabolism.
Active vitamin D in metabolismAlong with PTH, active vitamin D (1,25-dihydroxyvitamin D3), is also required in the metabolism of the bone remodelling, especially resorption. Active vitamin D increases the dietary absorption of the mineral. It also increases the renal reabsorption of calcium in the urine. The source vitamin D is food. In the skin vitamin D is formed after exposure to sunlight/ultraviolet light.
Calcitonin and homeostasisThe parafollicular cells (C-cells) of the thyroid gland secrete calcitonin, a 32-amino acid polypeptide hormone regulator of homeostasis.
|Interesting topics: Nutritional deficiency diseases | Mineral deficiency diseases | Vitamin deficiency diseases | Deficiency of carbohydrates | Deficiency of fats | Protein deficiency diseases | Magnesium deficiency diseases|
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3.Gregory R. Mundya and Theresa A. Guise. Hormonal Control of Calcium Homeostasis. Clinical Chemistry August 1999 vol. 45 no. 8 1347-1352.