The parathyroid glands, the size of a pinhead and shaped like a bean, are located on the neck, next to the thyroid gland. There are typically four glands, but some people can also have a fifth parathyroid gland. The parathyroid gland produces parathyroid hormone (PTH), which regulates the calcium balance in the body.
Parathormone has three kinds of effects on calcium in the body. It increase the release of calcium from the bone by activating bone-resorbing cells, increases the activation of vitamin D in the kidneys, and reduces the secretion of calcium from the kidneys (this, in turn, increases the secretion of phosphate from the kidneys). Increasing vitamin D increases the absorption of calcium from the intestines and therefore increases the amount of calcium in the blood.
When the level of calcium decreases, the parathyroid glands produce more parathormone into the bloodstream and the balance is restored. Correspondingly, when the level of calcium in the blood increases, the level of parathormone decreases. Parathormone has a short life in the bloodstream; the amount of the hormone halves in less than 5 minutes.
When should PTH be measured?
PTH can be measured when investigating abnormal calcium or phosphate levels or when suspecting that parathyroid gland function is not normal. The symptoms of an overactive parathyroid gland (hyperparathyroidism) are often quite subtle. In hyperparathyroidism, the PTH level in the blood is elevated.
Measuring the level of parathormone can be appropriate in connection with the following symptoms:
- Decreased memory function
- Muscle stiffness and rigidity
- Stomach pain
- Urinary stones
- Increased nerve irritability
- Stinging in the fingers and toes
- Numbness around the mouth
- Muscle cramps and convulsions
What does a PTH test measure?
The test measures the level of the PTH hormone in the blood. PTH, calcium, phosphate, magnesium, and vitamin D each influence the regulation of the amounts of the others. If the balance among them is disturbed, this also causes changes in the levels of the others.
How to interpret the PTH results?
Normally, the result is:
- 15.0-65 ng/l)
The PTH result must be assessed relative to the simultaneously measured calcium (S-Ca) concentration. If the PTH and Ca results are within the reference range, calcium regulation probably functions in the normal way in the body.
The levels of vitamin D (S-D-25), phosphate (S-Pi), alkaline phosphatase (S-AFOS), and creatinine (S-Krea) should also be examined when investigating calcium balance.
Please contact your physician or other healthcare professional if you suspect an illness or need help interpreting the results.
The reference values of this examination have changed 11.10.2021. You will find your own result's reference values from My LOUNA in touch with the graph. Read more about defining reference values.
What can cause elevated levels in the PTH?
When the parathyroid gland produces too much parathormone (hyperparathyroidism), the condition can be divided into primary and secondary hyperparathyroidism. In primary hyperparathyroidism, the overproduction of parathormone is caused by a tumour in the parathyroid gland, which can also be present in several parathyroid glands. An excessive amount of parathormone can cause hypercalcaemia, or an excessive amount of calcium in the blood.
Secondary hyperparathyroidism can be caused by kidney failure. Kidney disease has a negative impact on the formation of the active form of vitamin D. The lack of vitamin D impairs the absorption of calcium in the intestines. Therefore, the blood level of phosphate increases, the amount of calcium decreases, and the level of parathormone increases. Secondary hyperparathyroidism, or overproduction of parathormone, can also be caused by an intestinal disease, which leads to calcium malabsorption and vitamin D deficiency.
What can cause decreased levels in the PTH?
Hypoparathyroidism (underactive parathyroid) is a rare condition. Hypoparathyroidism causes low parathormone levels, which results in a low level of calcium, known as hypocalcaemia. Hypoparathyroidism can be caused by a thyroid gland surgery in which the parathyroid glands have been damaged or accidentally removed, for example.
The most typical additional PTH tests:
- Vitamin D deficiency is a problem for many Finns (1220 D-25)
- Calcium is critical for all cells of the body (2013 S-Ca, 6032 S-Ca-Albk)
- Creatinine indicates kidney function (2143 S-Krea)
- Phosphate is an important building block of bones, cells, and DNA (1432 fS-Pi)
- Alkaline phosphatase is elevated in liver and bone diseases (1046 S-AFOS)
SYNLAB test list: Parathormone (fP-PTH) https://www.yml.fi/tuotekuvaus_show.php?tuotenro=292
Terveyskirjasto health library: Lisäkilpirauhasen liikatoiminta (hyperparatyreoosi) https://www.terveyskirjasto.fi/terveyskirjasto/tk.koti?p_artikkeli=dlk01071&p_hakusana=parathormoni
LabTest online: PTH https://labtestsonline.org.uk/tests/pth
Suomen Kilpirauhasliitto: Lisäkilpirauhaset (Eeva Ryhänen) https://kilpirauhasliitto.fi/lisakilpirauhaset/
Suomen Kilpirauhasliitto: Lisäkilpirauhassairaudet https://kilpirauhasliitto.fi/lisakilpirauhassairaudet/
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