What is the parathyroid hormone?

The parathyroid hormone (PTH or PHT) is a hormone that is produced by four glands located in the neck, behind the thyroid. This hormone is delegated to maintain constant levels of calcium circulating within the human body. Calcium is important not only for the health of our bones, but also for the transmission of nerve impulses, muscle contractions, hormone secretion and other chemical and enzymatic reactions. Calcium is the most abundant mineral element in the human body. Approximately 98% of the 1200 g of calcium in adults is in the form of hydroxyapatite in the skeleton.

Parathyroid hormones are made by the parathyroid glands in the human body, which are four glands (pea sized), that lie behind the thyroid gland. If the level of blood calcium is too low, then the parathyroid glands release more parathyroid hormones into the body. This in-turn causes the bones to release more calcium into the bloodstream and therefore reduces the amount of calcium released by the kidneys into the urine. Vitamin D is also converted to a more active form, which causes the intestines to absorb more calcium and phosphorus. However if the level of calcium is too high, then the parathyroid glands release less of the parathyroid hormone, and thus the whole process is reversed.

Parathyroid hormone levels that are either too low, or too high can lead to problems with the kidney, bones, and can cause changes in calcium and vitamin D levels within our body.


Why measure the level of parathyroid hormone?

The examination on the parathyroid hormone, must be combined with other diagnostic tests, such as those that determinate the levels of calcium circulating in the body, as wells as the quantities of phosphorus and vitamin D. It uses these tests in the presence of signs or symptoms which suggest an altered calcium metabolism, for example this is present in post-menopausal women with a framework of osteopenia or osteoporosis, or in response to an incidental finding of altered levels of calcium in the body. It is also used in patients with chronic renal failure.

The patients that are tested, may be affected by primary hyperparathyroidism or secondary hyperparathyroidism, however it is also used in patients that have hypocalcemia, as well as in the case of a suspected malfunction of the parathyroid glands and thus reduced levels of circulating PTH within the body.


Standard of preparation

Sampling is usually done in the morning in the hospital. The doctor will advise and recommend if you need to be fasting prior to the blood examination. In this case it is recommended that the patient does fast prior to the exam, and arrives with an empty stomach. You should inform your doctor of any medication you are taking prior to the exam, as some medical treatments may interfere with the blood results.


Is the examination painful or dangerous?

The examination is neither painful nor dangerous. The patient may feel a tingling sensation with the entrance of the needle in the arm when blood is being extracted for examination.


How is the exam performed?

The exam consists of a simple blood sample test.