ABSTRACT

When inadequate calcium is absorbed or present in the diet, the calcium levels of the tissues and fluids are maintained by calcium removed from bone. Interest in calcium nutritional status has increased as investigations have indicated an association of an adequate intake of calcium with a lowered risk of osteoporosis and of essential hypertension. Osteoporosis represents a condition that relates to past long-term calcium losses, where bone resorption exceeds bone formation. Hypocalcemia as seen in the clinic is rarely caused by a dietary deficiency of calcium, but rather by disorders of calcium metabolism, most commonly with hypoparathyroidism. When hypercalcemia occurs, calcitonin is released by the thyroid gland, which promotes the uptake of calcium by bone and induces blockage of bone resorption or breakdown. Obligatory urinary losses of calcium occur even under condition of low dietary intake and low calcium status.