Overactivity of the
parathyroid glands, causing parathyroid
hormone to be produced in amounts greater than normal. Parathyroid hormone controls the level of calcium in the blood, and
overproduction of the hormone
leads to a rise in blood calcium. If this is great, the
person complains of exhaustion, depression, loss of appetite,
weakness nausea, vomiting, constipation, and occasionally excessive thirst.
Calcium is removed from the bones; pain and
tenderness may follow, and the bones (being fragile) are more prone to fracture. This may lead to a diagnosis of the condition, since the X-ray appearances of the
bones alter.
Increased
excretion of calcium in the urine often leads to the formation of
kidney stones; about 5
percent of persons with
kidney stones are likely to show features of hyperthyroidism.
There are four parathyroid glands, one pair situated on each side of the thyroid gland, and they are
normally about the size of a pea. Overactivity may be due to the development of a
tumor of one of the glands (
primary hyperparathyroidism) or may be the
result of a chronically low level of calcium in the blood---such as
occurs in kidney disease or deficient absorption of
calcium from the intestine.
Treatment of primary hyperparathyroidism is surgical removal of the tumor; treatment of
secondary hyperparathyroidism requires correction of the underlying condition. It is possible to
raise the blood calcium
level by reducing the
phosphate level, so that in chronic kidney failure a diet low in
protein and phosphorus, with
added aluminum hydroxide and
vitamin D, may be recommended.