The PTH exam is requested in order to assess the functioning of the parathyroid glands, which are small glands located in the thyroid that have the function of producing the parathyroid hormone (PTH). PTH is produced in order to prevent hypocalcaemia, that is, low concentrations of calcium in the blood, which can lead to seizures and heart failure in more severe cases and when there is no treatment. Learn more about what hypocalcemia is and what it can cause.
This test does not require fasting and is done with a small blood sample. The PTH dosage is requested mainly to diagnose hypo or hyperparathyroidism, but it is also required in the follow-up of patients with chronic renal failure, and is usually requested together with the blood calcium dosage. In people without any change in parathormone production, normal blood values should be between 12 and 65 pg / mL, which may vary according to the laboratory.
Although preparation is not necessary before the exam, it is important to inform the doctor about the use of any medication, especially sedatives, such as Propofol, for example, as they can decrease the concentration of PTH, thus interfering with the interpretation of the result by the doctor. In addition, it is recommended that the collection be made in a reliable laboratory or hospital with trained professionals, since hemolysis, which is often caused by errors in the collection, can interfere with the test result.
How the exam is done
The exam does not need any preparation, however it is recommended that the collection be made in the morning, as its concentration may vary throughout the day. The collected blood is sent to the laboratory, where it is processed and placed in a device where the analyzes are made. The result is usually released about 24 hours after collection.
Parathyroid hormone is produced in response to low blood calcium concentrations. It acts on the bones, kidneys and intestines in order to increase the availability of calcium in the blood and prevent hypocalcaemia. In addition, PTH is responsible for increasing the absorption of vitamin D from the intestine.
PTH activity is regulated by another hormone, calcitonin, which begins to be produced when calcium levels are too high, thus decreasing PTH production and stimulating the excretion of calcium in the urine, for example. Understand how it is done and what the calcitonin test is for.
What can the result mean
The test result is interpreted by the doctor together with the calcium dosage, since the production of parathormone depends on the concentration of calcium in the blood.
- High parathyroid hormone: It is usually indicative of hyperparathyroidism, especially if the blood calcium level is high. In addition to hyperparathyroidism, PTH may be elevated in the case of chronic renal failure, vitamin D deficiency and hypercalciuria. Understand what hyperparathyroidism is and how to treat it. Low parathyroid hormone: Indicates hypoparathyroidism, especially if blood calcium levels are low. Low or undetectable PTH can also be indicative of autoimmune disease, incorrect development of the glands or after surgical procedures. See what hypoparathyroidism is and how to identify it.
The PTH test is requested by the doctor when there is suspicion of hypo or hyperparathyroidism, before and after performing surgical procedures involving the thyroid or when there are symptoms of hypo or hypercalcemia, such as fatigue and abdominal pain, for example. Find out what are the main causes of excess calcium in the blood and how to treat it.
