Most people have four glands each the size of a grain of rice called the parathyroid located on the back of the thyroid gland.
Although their names are similar, the thyroid and parathyroid are completely different. The parathyroid glands produce the parathyroid hormone (PTH) and work like a thermostat that maintains calcium balance. When calcium levels in blood are too low, parathyroid hormones are released in order to return it to normal levels. When calcium levels are normal or slightly elevated, the parathyroids stop releasing parathyroid hormones. A proper balance of calcium is crucial for normal functioning of the heart, nervous system, kidneys and bones.
If the parathyroid glands produce too much or too little hormone, the balance is disturbed. If they secrete too much parathyroid hormones, this leads to hyperparathyroidism and the calcium level in blood increases. In many cases, a benign tumour of the parathyroid causes increased activity. In other cases, excess hormones may be caused by enlarged parathyroid glands. In rare cases, the cause is cancer.
If a sufficient amount of parathyroid hormone is not produced, this is called hypoparathyroidism. The blood will contain very little calcium and excess phosphorus. Among the causes are injury to the glands, endocrine disorders and genetic conditions. Treatment attempts to recover the balance between calcium and phosphorus.
Hyperparathyroidism and hyperparathyroidism
Excess in the function of the parathyroid glands is known as hyperparathyroidism, and is usually associated with elevated plasma levels of calcium and bone fragility, which causes greater susceptibility to fractures. Insufficient function of the parathyroid gland (hypoparathyroidism) is much less common, and usually occurs after surgery on the thyroid gland, which entails the existence of hypocalcaemia.
There are some other rare diseases, which appear to be due to alterations in the receptor for parathyroid hormone, such as Jansen's metaphyseal chondrodysplasia and Blomstrand's chondrodysplasia.
For more information visit:
What is high blood calcium?
http://www.hormone.org/questions-and-answers/2012/hypercalcemia
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