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What is parathyroid hormone (PTH)?

Dr. Jack Merendino, MD
Endocrinology Diabetes & Metabolism
Parathyroid hormone (PTH) is a key regulator of calcium and bone metabolism. PTH is made by the parathyroid glands which are located in the neck, just adjacent to the thyroid, though their function is completely separate from the thyroid. Most people have 4 glands, two on each side, one near the upper end of the thyroid gland on that side and one near the lower. Occasionally the glands may be found outside of their usual location, because they start out in one location during embryonic development and migrate or move as the fetus matures. Occasionally a parathyroid gland will seemingly get “stuck” somewhere along that migratory path. This is important only when a gland becomes overactive and needs to be removed surgically. It may be difficult to find a gland in an unexpected location unless you are a very skilled surgeon or do just the right radiographic tests to locate the gland. 

The main role of PTH is to help keep the blood calcium level normal. This is critical because many physiologic processes require a precise calcium level in the blood. When the level of calcium in the blood starts to fall, the parathyroid glands release additional PTH.  PTH does three main things: 
  1. PTH increases the amount of active vitamin D in the body, which results in more calcium being absorbed from the food we eat.
  2. PTH causes the release of stored calcium from bone into the bloodstream.
  3. PTH causes calcium to be absorbed back into the body from urine that is being made. 
These three actions together result in an increase in blood calcium levels. 

Parathyroid hormone is used as a medication in two settings. First, one form of synthetic parathyroid hormone (drug name Forteo) is used to treat osteoporosis. Second, another form of parathyroid hormone (drug name NetPara) is used to treat hypoparathyroidism -- a condition of too little parathyroid hormone in the body. Hypoparathyroidism usually results from the accidental removal of all 4 parathyroid glands when one undergoes thyroid surgery, though there are other causes as well.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.