Parathyroid hormone (PTH) – functions, indications for examination, causes of deficiency and excess

Proven content

Parathyroid hormone (PTH) is an important polypeptide hormone produced in the parathyroid glands. It is a substance that largely regulates the calcium and phosphorus balance of our body. Abnormal PTH values ​​- both increased and lowered parathyroid hormone – may indicate the emergence of serious health problems. What is worth knowing about the influence of parathyroid hormone on the functioning of the body? When should a PTH test be performed and how to interpret its results?

Parathyroid hormone (PTH) – characteristics

Parathyroid hormone, also abbreviated as PTH (from the English “parathyroid hormone” – parathyroid hormone) is a polypeptide hormone that consists of 84 amino acids. The parathyroid glands are responsible for its production – small glands located paired next to the thyroid gland, more precisely: in the vicinity of the lower and upper poles of the thyroid gland.

Also check: Peptide structurally similar to parathyroid hormone (PTHrP, parathytoid hormone related peptide)

Parathyroid hormone (PTH) – functions

Parathyroid hormone regulates the phosphate and calcium balance in the body. Although the parathyroid glands constantly produce this substance, it is not excreted into the body immediately. The release of PTH is conditioned by the concentration of calcium ions in the blood serum. When it is lowered, PTH is released to regulate blood calcium levels. How? To this end, parathyroid hormone acts on the bones, where the release of calcium into the blood is increased.

Another area of ​​action of PTH is the kidneys, where it also focuses on maintaining the balance of calcium and phosphate. Parathyroid hormone increases calcium reabsorption and, at the same time, inhibits the reabsorption of phosphate in the renal tubules. This is important because the phosphate normally combines with calcium into various salts, thus limiting the concentration of “pure” calcium in the blood. Thus, by stimulating the excretion of phosphate in the urine while preserving calcium ions, PTH increases the level of calcium in the blood.

An important task of PTH is also to participate in the formation of biologically active forms of vitamin D3. Parathyroid hormone is responsible for stimulating an important enzyme – 1-alpha-hydroxylase – thanks to which vitamin D3 precursors can be converted into an active vitamin. In this way, PTH also indirectly increases the intensity of the intestinal absorption of calcium into the body, supported by vitamin D.

Also read: Calcitonin (CT) – what is this test?

Parathyroid hormone (PTH) – indications for the examination

The PTH test is an important element in the diagnosis of various diseases and conditions. Increased or lowered parathyroid hormone often helps to confirm or rule out a medical hypothesis.

Indications for PTH testing occur if there is a suspicion of diseases and disorders such as:

1. hypercalcemia (too high calcium levels);
2. hypocalcemia (too low calcium);
3. hypoparathyroidism;
4. hyperparathyroidism;
5. neoplastic diseases (tumors that produce parathyroid hormone);
6. phosphate disorders;
7. poisoning with vitamin D as a result of its overdose;
8. osteoporosis;
9. gastric ulcer and duodenal ulcer;
10. kidney diseases (including nephrolithiasis);

The test to determine the level of PTH is also performed in patients who have undergone surgery to remove the parathyroid glandsto assess its effectiveness. Moreover, the concentration of PTH is constantly monitored in people undergoing hemodialysis.

A doctor may also order a PTH test if a patient has symptoms that are unrelated to other causes, such as muscle weakness, headaches, difficulty concentrating, nausea and vomiting, or depressed mood. Such a set of symptoms is often related to hypercalcemia.

Parathyroid hormone (PTH) – what does the test look like?

The PTH test is a laboratory test based on the analysis of a blood serum sample taken from the blood of the elbows. The downloaded material is sent for further analysis at the diagnostic center. Plasma must be separated rapidly from blood cells after blood is drawn and before parathyroid hormone measurement is performed. The sample can be kept in the refrigerator for a maximum of 24 hours. Longer storage of the sample requires its freezing, up to a maximum of 2 hours from collection.

The concentration of PTH is determined from plasma or serum using radioimmunoassay methods or non-isotope immunochemical methods with automatic analyzers. Usually, the waiting time for the parathyroid hormone test result is 1 day.

For the obtained result to be meaningful, the patient must undergo the test on an empty stomach, without having previously taken food or drink for at least 8 hours. You should also consult your doctor about medications, vitamins and dietary supplements that may affect the test result.

Parathormon (PTH) — norma

The generalized norm of PTH for an adult is 20-30 pg / ml. However, it is worth knowing that the standards of PTH are influenced by several factors, including age, sex, study population and method of determination. For this reason, the PTH result should always be consulted with your doctor. The results of the PTH test are almost always interpreted together with the results of the blood calcium and phosphate tests – the parathyroid hormone result alone does not provide enough information to confirm or rule out any diagnosis.

Increased parathyroid hormone – causes and effects

Excess parathyroid hormone can be associated with a variety of disease states. Most often, increased parathyroid hormone indicates such disorders as:

1. primary hyperparathyroidism, resulting from the appearance of PTH-producing nodules in this organ (in this case, elevated PTH levels are also accompanied by hypercalcemia, i.e. excessive calcium levels in the blood);
2. secondary hyperparathyroidism, e.g. as a result of acute or chronic renal failure accompanied by hypocalcemia, and thus insufficient calcium in the blood;
3. neoplastic diseases, especially lung tumors and breast tumors, which are capable of producing PTH or other substances with very similar action and characteristics;
4. vitamin D poisoning by overdosing.

It is necessary if the level of PTH in the body is too high further diagnostics and appropriate treatment the problem that underlies elevated parathyroid hormone. The prolonged state of elevated PTH in the blood may lead to further serious problems, for example:

1. bone weakness and the risk of developing osteoporosis caused by the increased reabsorption of calcium from bone tissue;
2. disorders of the cardiovascular system;
3. fertility problems resulting from disturbances in the functioning of the endocrine system.

Also read: Hyperparathyroidism associated with low calcium intake

Lowered parathyroid hormone – causes and effects

What can a reduced PTH level mean? Most often, this is the case with hypoparathyroidism (but it is worth being aware that this disease is much rarer than their hyperparathyroidism). Typically, this problem is caused by complications and complications following head and neck surgeries, such as complete removal of the thyroid gland (thyroidectomy).

Other injuries and damage to the parathyroid glands can also be involved. Then low PTH levels are usually accompanied by a calcium or vitamin D deficiency. Lowered parathyroid hormone may also be the result of long-term radiotherapy or accompany various types of cancer.

People with long-term PTH levels that are too low often develop tetany. These are uncontrolled contractions of various muscle groups that result from too low concentration of calcium ions in the blood. Progressive tetany is a troublesome disease that significantly impedes everyday functioning. If parathyroid hormone is lowered, it is worth performing more extensive diagnostic tests and appropriate treatment of the cause of this condition, so as not to expose yourself to further health problems.

Also check: Thyroid doctor – endocrinologist or thyroidologist?

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