Description: PTH is a hormone that is used to help maintain levels of calcium in the blood. A PTH test will measure the amount of PTH in the blood and can be used to make sure that the feedback loop is working correctly.
Also Known As: Parathyroid hormone Intact test, Intact PTH test, Parathormone test
Collection Method: Blood Draw
Specimen Type: Plasma
Test Preparation: No preparation required
When is a PTH test ordered?
When a calcium test is abnormal, a PTH test may be requested. When someone shows signs of hypercalcemia or hypocalcemia, it may be prescribed.
When someone has been treated for an illness or condition that affects calcium control, such as the elimination of a parathyroid tumor, or when a person has a long - term condition like renal disease, a health practitioner may prescribe a PTH test along with a calcium test at intervals.
When someone with hyperparathyroidism is undergoing surgery to remove abnormal parathyroid tissue, an intraoperative PTH test may be done to confirm that all of the abnormal glands are removed, which can vary in number and position.
What does a PTH blood test check for?
The hormone parathyroid aids in the body's ability to keep calcium levels in the blood at a constant level. Calcium, PTH, vitamin D, and, to a lesser extent, phosphorus and magnesium are all part of a feedback loop. Conditions and disorders that disturb this feedback loop can lead to abnormal increases or declines in calcium and PTH levels, as well as hypercalcemia and hypocalcemia symptoms. This test determines how much PTH is present in the blood.
PTH is generated by four parathyroid glands, which are positioned behind the thyroid gland in the neck and are the size of a button. PTH is secreted into the bloodstream by these glands in reaction to low blood calcium levels. To help restore normal blood calcium levels, the hormone functions in three ways:
- PTH encourages calcium to be released from the bones into the bloodstream.
- It encourages the kidneys to convert vitamin D from inactive to active form, which enhances calcium absorption from food in the intestines.
- It works on the kidneys to reduce calcium excretion in the urine while increasing phosphorus excretion.
PTH generally declines as calcium levels in the blood begin to rise.
The parathyroid hormone is made up of 84 amino acids. The parathyroid gland contains both intact and fragmented hormone, which it secretes. The intact hormone makes up a lesser percentage of the total, but its proportion rises when calcium levels are low and falls when calcium levels are high.
PTH has a relatively short half-life once released into the bloodstream; absorption and cleavage in the liver and kidneys cause levels to drop by 50% in less than 5 minutes. The pieces are known as C-terminal fragments, and they range in size from 6 amino acids to more than half of the molecule's N-terminal region. C-terminal fragments have a longer half-life, are found in higher concentrations, and are eventually eliminated by the kidneys. Although the C-terminal fragments were assumed to be inactive at first, it now appears that some of them may have biologic actions that are able to counteract those of whole PTH.
Lab tests often ordered with a PTH test:
- Vitamin D
Conditions where a PTH test is recommended:
- Parathyroid Disease
- Kidney Disease
How does my health care provider use a PTH test?
The most commonly requested parathyroid hormone test is intact PTH. It's utilized to figure out what's causing a low or high calcium level, as well as to distinguish between parathyroid and non-parathyroid reasons. When a person has a parathyroid-related ailment, it can also be utilized to track the effectiveness of treatment. People with chronic renal disease or who are on dialysis have their PTH levels checked on a regular basis.
Almost always, a calcium test is ordered in conjunction with a PTH test. It's not just the calcium level in the blood that matters, but also the calcium-PTH balance and the parathyroid glands' response to fluctuating calcium levels. Typically, health professionals are concerned about severe calcium regulation imbalances that may necessitate medical intervention or recurring imbalances that signal an underlying disease.
PTH levels can be used to track persons who have chronic calcium imbalances due to illnesses or diseases, as well as those who have had surgery or another procedure for a parathyroid tumor.
What do my PTH test results mean?
A health professional will look at both calcium and PTH findings to see if they're in the right range and in balance. If both PTH and calcium levels are normal, the body's calcium regulating mechanism is likely to be in good working order.
Low levels of PTH can be caused by hypercalcemia or a defect in PTH generation, resulting in hypoparathyroidism. Hyperparathyroidism, which is most commonly caused by a benign parathyroid tumor, can produce excessive PTH secretion. Cancer may be the reason in some cases.
If calcium levels are low and PTH levels are high, the parathyroid glands are responding properly and producing enough PTH. A health practitioner may examine a low calcium level further by analyzing vitamin D, phosphorus, and magnesium levels, depending on the degree of hypocalcemia.
If calcium levels are low and PTH levels are normal or low, PTH isn't working properly, and the person being tested is most likely hypoparathyroid. The failure of the parathyroid glands to produce enough PTH causes hypoparathyroidism. It could be caused by a variety of factors and could be chronic, progressive, or transitory. An autoimmune problem, parathyroid injury or removal during surgery, a hereditary condition, or a serious sickness are all possible causes. PTH levels will be low, calcium levels will be low, and phosphorus levels will be high in those who are impacted.
If your calcium levels are high and your PTH levels are high, your parathyroid glands are producing too much PTH. To help diagnose the origin and severity of hyperparathyroidism, a health practitioner may order X-rays or other imaging procedures. Primary, secondary, and tertiary hyperparathyroidism are three types of hyperparathyroidism characterized by an excess of PTH produced by the parathyroid glands.
If calcium levels are high and PTH levels are low, the parathyroid glands are functioning normally. However, a health practitioner will likely conduct additional tests to rule out non-parathyroid causes for the elevated calcium, such as genetic variants in calcium receptors or tumors that secrete a peptide with PTH-like activity, which increases calcium concentration while decreasing PTH.
We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.