Definition of Secondary hyperparathyroidism:

Secondary hyperparathyroidism is when the parathyroid glands in your neck produce too much parathyroid hormone (PTH) because your calcium levels are too low.

See also:

• Hyperparathyroidism
• Primary hyperparathyroidism

Causes, incidence, and risk factors:

The parathyroid glands help control calcium use and removal by the body. They do this by producing parathyroid hormone, or PTH. PTH helps control calcium, phosphorus, and vitamin D levels within the blood and bone.

When calcium levels are too low, the body responds by increasing production of parathyroid hormone. This increase in parathyroid hormone causes more calcium to be taken from the bone and more calcium to be reabsorbed by the intestines and kidney.

Medical conditions that cause low blood calcium levels or interfere with the body's ability to break down and remove phosphate can lead to secondary hyperparathyroidism. Too much phosphate causes changes in calcium levels.

Kidney failure is a common cause of secondary hyperparathyroidism. Kidney failure can interfere with the body's ability to remove phosphate.

Other causes of secondary hyperparathyroidism may include:

• Calcium deficiency
  • Not enough calcium in the diet
  • Too much calcium loss in the urine
• Conditions that make it hard for the body to break down phosphate, including:
  • Aluminum poisoning
  • Certain types of cancer
  • Kidney disease
  • Malnutrition
  • Malabsorption
• Vitamin D disorders (often seen in children with malnutrition and older adults who do not get enough sunlight):
  • Problems absorbing vitamin D into the body (malabsorption)
  • Problems breaking down vitamin D (due to the use of certain drugs)
  • Rickets
  • Too little vitamin D (deficiency)