Parathyroid hormone (also called parathyroid hormone, parathyrin) is a hormone produced by the tissue of the parathyroid (parathyroid) glands that are located on the anterolateral side of the neck. They are located behind the thyroid gland, closely adjacent to its posterior surface and to the lower part of both its lobes. Parathyroid hormone by its chemical nature is a complex protein substance - a polypeptide, a derivative of amino acids.
Its main function is the participation and regulation of calcium-phosphorus metabolism in the body. The blood calcium and secretion of parathyroid hormone are directly dependent on each other. The hormone is able to increase the concentration of calcium through exposure to bone tissue, kidney and gastrointestinal tract. In bone tissue, parathyrin promotes an increase in the yield of the soluble part of the mineral from it by stimulating the synthesis of specialized enzymes that are responsible for the breakdown of bone material. Bone tissue under the influence of parathyroid hormone undergoes resorption and calcium ions enter the bloodstream. Together with calcium metabolism, parathyroid hormone helps regulate the level of phosphate in the body. Reducing the intensity of the first biological process, it enhances the course of the second. In addition, this hormone is involved in enhancing the synthesis of calcitriol in the intestines, helping calcium reabsorption. Parathyroid hormone takes an indirect part in regulating the activity of all calcium-dependent enzymes in the reactions catalyzed by them. The coagulation system of blood also falls under its influence.
If parathyroid hormone is elevated, then severe endocrine diseases are formed associated with a violation of the integrity of the bones - hyperparathyroidism and osteoporosis. As a result of this physiological deficiency, the level of calcium in the blood decreases sharply, which leads to increased neuromuscular excitability. Concomitant diseases in this case may be an increased content of alkalis in the body and the development of renal failure. By reducing the calcium content in the lens of the eye, cataracts occur.
The level of the parathyroid hormone in the blood follows a circadian rhythm. The basal level is set at about 8 o’clock in the morning, while at 14-16 hours of the day, when a person is at the peak of activity, parathyroid hormone is elevated. A blood test for the amount of parathyrin is carried out by immunochemiluminescence. It must be done on an empty stomach, while one or two days before blood sampling exclude the intake of alcohol and heavy physical activity, do not smoke a few hours before the procedure.
Parathyroid hormone analysis is prescribed only when the patient has suspicions of the existence of diseases such as hyper- and hypocalcemia, urolithiasis and neurofibromatosis. Also, indications for the purpose of the analysis can be: osteoporosis, pseudo-fractures of long bones, any physiological changes in the bones or osteosclerosis of the vertebral bodies, as well as a suspicion of multiple endocrine neoplasia type 1 and 2 (MEN 1.2). For parathyroid hormone, the norm for an adult is considered to be 9.5-75 pg / ml. This applies to both men and women of reproductive age. If it is revealed that parathyroid hormone is elevated, then there is every reason to assume that the patient has primary, secondary, tertiary hyperparathyroidism, pseudohypoparathyroidism or Zollinger-Ellison syndrome.
Under primary hyperparathyroidism , hyperplasia of the parathyroid glands, cancer of the gland tissue and endocrine neoplasia of two types are combined. Secondary hyperparathyroidism includes chronic renal failure, hypervitaminosis D, ulcerative colitis, rickets, Crohn's disease. If parathyroid hormone is elevated, then the analysis, as a rule, is done together with the determination of the level of calcium in the blood and in the future, two indicators are compared and the dependence is detected.