parathyroid gland

one of four small glands, located behind or within the THYROID GLAND , that control the METABOLISM of calcium and phosphorus (as phosphate) in the body. The HORMONE responsible, parathormone (or simply parathyroid hormone), is produced and released by the glands. A deficiency of the hormone leads to lower levels of calcium in the BLOOD , with a relative increase in phosphorus. This produces tetany, a condition involving muscular spasms that can be treated by injection. This is also known as hypoparathyroidism and is often caused by the removal or injury of the glands during THYROIDECTOMY . If the hormone is at high levels, calcium is transferred from bones to the blood, causing weakness and susceptibility to breaks.