Synonym: Parathormone, PTH.

Parathyroid Hormone (PTH) is a hormone produced by the parathyroid gland when the level of calcium decreases. Its function is to maintain and control the calcium level. Therefore, when the calcium level drops, PTH promotes the mobilization of calcium from bone into the bloodstream and also enhances renal tubular reabsorption of calcium and reduces phosphate reabsorption, which in that way will reducing calcium excretion and increasing phosphate excretion by the kidneys.

The main function of PTH hormone is maintaining the sufficient levels of calcium in the blood, as a result, it has ways of effects on kidney, the first way of effect work through reducing the renal secretion of hydrogen ions that finally lead to increase renal excretion of bicarbonate and chloride; while the other way of renal controlling calcium level by the action of PTH that works through promoting and increase of renal production of active vitamin D metabolites that causing increased calcium absorption in the small intestine.

PTH has a short circulating half-life which about 5 min because it uptake and cleavage in the liver and kidneys. The fragments are referred to as C-terminal that have variable size, longer half-life, higher concentrations, and also larger than N-terminal portion. Intact and N-terminal PTH are the only biologically active forms found in very low concentration comparing to inactive  C-terminal and midregion fragments that account for about 90% of circulating PTH. 

The parathyroid hormone test measures the level of parathyroid hormone in the blood. The result of a parathyroid hormone test may Increase or decrease which indicates the presence of certain conditions that may require treatment.

There are many reasons to do the parathyroid hormone (PTH) test, for example, the PTH test used to assess the causes and sources of abnormal calcium levels, to distinguish between parathyroid-related and nonparathyroid-related to hypercalcemia. In addition, the PTH test used to diagnose and differentiate between hyperparathyroidism types, and also diagnose hypoparathyroidism. PTH test acts as an indicator to detect accidental damage or unwitting removal of the parathyroid glands during thyroid or neck surgery as well as the PTH test used to evaluate parathyroid glands destruction by the action of autoimmune. As for monitoring, the PTH test used to evaluate the response of the parathyroid gland to altered serum calcium levels in certain cases like that result from malignant processes that lead to decreased PTH production.

The parathyroid hormone test does not need any preparation steps by the patient. Besides, it must be taken into consideration the time of the test because there is a fluctuation in the levels of parathyroid hormone during different parts of the day; for example, the level of parathyroid hormone peaked during the sleeping period and also the lowest level during the period between the mid-morning and late afternoon. Furthermore, the parathyroid hormone with different sessional as it relates to Vitamin D.

Reference values:

*Normal ranges may vary from one lab to another due to several factors, so it is important to discuss test results with a doctor.

Interpretation

The highest level of parathyroid hormone may present in specific diseases such as Fluorosis, hyperparathyroidism, Pseudohypoparathyroidism, Kidney disease, vitamin D deficiency, Pseudogout, and Zollinger-Ellison syndrome. In addition, PTH Levels may decrease in some diseases like autoimmune destruction of the parathyroids, DiGeorge syndrome, Hyperthyroidism, Hypomagnesemia, Nonparathyroid hypercalcemia, Sarcoidosis, an overdose of vitamin D, and secondary hypoparathyroidism due to surgery.

The parathyroid hormone test is often performed by draw a blood sample from a vein of the patient’s arm to analyze and measure the amount of parathyroid hormone in the sample of (1mL) volume. The method most probably used to detect the amount of parathyroid hormone is immunoassay.

A healthcare provider may be ordered several blood tests like blood calcium, phosphorus (phosphate), magnesium, vitamin D, and others along with a PTH test to help detect and diagnose the condition.

The result of a parathyroid hormone test may Increase or decrease which that indicate presence of certain conditions that may require treatment.

The parathyroid hormone (PTH) is a hormone produced by the parathyroid gland to maintain and control of calcium level. Furthermore, the PTH test is very important because it is useful in differential diagnosis hypercalcemia, hyperparathyroidism types, and also a diagnosis of hypoparathyroidism as well as investigates if there is an accidental damage or unwitting removal of the parathyroid glands during thyroid or neck surgery. In general, the highest and lowest level of parathyroid hormone may be associated with specific diseases such as Fluorosis, Hypomagnesemia, Nonparathyroid hypercalcemia, and Sarcoidosis.

Actually, the intact PTH assay is the most common assay for the test, it measures the whole molecule (PTH 1-84) and the larger fragments (predominantly PTH 1-74).