Calcium, osteoporosis and phosphate
Over 99 per cent of the adult body’s 1000–1200 g calcium is in the bones and teeth, yet the remainder, less than 1 per cent, plays an essential part in the functioning of many diverse vital activities such as the transmission of nerve impulses, excitability at the junction of nerve and muscle, clotting of blood, absorption of vitamin B12, maintenance and proper functioning of cell membranes, secretion of juices by cells, activation of enzymes and hormone
secretion. The calcium in the blood is kept within a very narrow concentration range, using the bones as a source of calcium when needed and as a depot for calcium when the blood concentration is rising. This careful control is achieved mainly by the interplay of several hormones, a rise in calcium being brought about by parathormone from the parathyroid glands in the neck, while a decrease in calcium in the blood is brought about by the hormone calcitonin secreted by the thyroid gland. The responsiveness of
bone to these hormones is affected by vitamin D, which is itself really a hormone even though it can be obtained in the diet. Many other hormones are also involved in the very elaborate system controlling the blood calcium concentration.
Calcium, osteoporosis and phosphate, Absorption of calcium, Hormone Replacement Therapy (HRT), Osteoporosis in men, Osteomalacia, Iron, Sources and requirements, Iron in infancy, Menstruation, Iron deficiency,Sodium, potassium and chloride, Sources and requirements, High blood pressure (hypertension), Potassium excess, Iodine, Fluoride,Sources, Fluoride supplements, Toxicity, Selenium, Requirements,Deficiency, Zinc, Copper and molybdenum, Magnesium, Aluminium,
cadmium, cobalt, germanium, manganese, nickel, silicon, strontium, sulphur and tin, Sources and requirements