Dorothy FarrarParathyroid
The parathyroid glands (Glandulae parathyroideae) are fourfold organs that produce the parathyroid hormone. Parathyroid hormone increases the level of calcium in the blood . Disorders of the parathyroid glands lead to hypocalcemia or hypercalcemia.
Definition
The parathyroid glands are also known as the epithelial bodies . These are endocrine, i.e. hormone-producing, glands . Parathyroid hormone is produced in the cells of the parathyroid glands. The parathyroid hormone is a peptide hormone and serves to increase the calcium level in the blood.
Diseases of the parathyroid glands lead to fluctuations in the concentration of calcium in the blood. If the parathyroid gland is overactive, the calcium level rises sharply. The result is what is known as hypercalcaemia. If the parathyroid glands are underactive, the calcium level in the blood is too low. It’s called hypocalcaemia.
Anatomy
As the name suggests, the parathyroid glands are usually located in close proximity to the thyroid gland . However, the location may vary. The organs, weighing 30 to 35 milligrams, are sometimes found behind the breastbone. Humans have a total of four parathyroid glands.
These are located near the upper and lower poles of the thyroid gland, respectively. The two upper or outer parathyroid glands are called the superior parathyroid glands, and the two lower or inner parathyroid glands are called the inferior parathyroid glands.
From an evolutionary point of view, the parathyroid glands come from the endoderm, the inner germ layer. The two upper parathyroid glands are created from the 4th pharyngeal pouch. The lower parathyroid glands, on the other hand, come from the 3rd pharynx. The thymus gland, for example, also arises from this pharyngeal pouch.
The epithelial bodies are surrounded by a connective tissue capsule for protection. Fine cuticles emanate from this. In this, the individual epithelial cells are arranged in strands. The epithelial cells can be divided into principal cells and oxyphilic cells. The main cells produce the parathyroid hormone. The function of the oxyphilic cells is not yet clear. What is certain, however, is that their number increases with age.
Function
The main function of the parathyroid glands is the production of parathyroid hormone. This is involved in regulating calcium and phosphate levels in the human body. When the calcium level in the blood falls, parathyroid hormone is released by the parathyroid glands.
Conversely, a calcium level above normal inhibits the secretion of parathyroid hormone. This process is also known as negative feedback. The parathyroid glands have calcium-sensitive receptors on their cell surface to measure blood calcium levels.
The parathyroid hormone has several indirect and direct mechanisms of action with which they can influence the calcium content in the blood.
Directly to the kidneys, the parathyroid hormone promotes calcium absorption and at the same time inhibits the reabsorption of phosphate. If the phosphate concentration is too high, the mobilized calcium would form a poorly soluble bond with the phosphate. Deposits of these calcium-phosphate complexes can cause nephrocalcinosis, a calcified kidney.
In addition, the hormone produced by the parathyroid glands in the kidneys stimulates the formation of calcitrol. Calcitrol is the most effective form of vitamin D and ensures increased calcium absorption in the small intestine and in the kidneys themselves. In the bone , parathyroid hormone stimulates the osteoclasts and thus stimulates osteolysis. This degradation of bone cells mobilizes calcium and phosphate.
However, since the parathyroid hormone stimulates phosphate excretion via the urine , as already mentioned , the calcium level in the blood rises, but the phosphate level remains constant. With a normal concentration of parathyroid hormone in the blood, the bones do not suffer any damage from the breakdown of calcium.
Diseases
- Hyperparathyreodismus
- Hypoparathyreodismus
An overactive parathyroid gland is called hyperparathyroidism. Hyperparathyroidism can be caused, for example, by tumors of the epithelium. During the disease, increased levels of parathyroid hormone are released into the blood. The result is increased parathyroid hormone and calcium levels in the blood. In hyperparathyroidism, the bone substance is damaged by the constant breakdown of calcium. Osteoporosis occurs .
Kidney stones form due to the increased excretion of calcium in the urine. Deposits of calcium and phosphate in the blood vessels lead to calcification and increase the risk of suffering a heart attack or stroke . As a rule, the diagnosis is made quite early, since the elevated calcium levels are quickly noticed in routine blood tests . Treatment is usually by removing the causative tumor.
Underactive parathyroid glands are also called hypoparathyroidism. The most common cause of the disease is accidental surgical removal of the parathyroid glands during thyroid surgery. Parathyroid hypofunction can also be caused by radiation, autoimmune diseases or a severe magnesium deficiency .
The symptoms are caused by the massive lack of calcium and an increased phosphate level in the blood. Calcium deficiency results in an increased susceptibility to cramps. Epileptic seizures can occur. A pawed position of the hands, which is caused by cramps in the arm and hand muscles, is characteristic of a severe calcium deficiency. Other symptoms include dry skin and hair loss . Hypoparathyroidism is usually treated with medication by administering calcium and vitamin D.
Hello and welcome to my Health Guide & Encyclopedia! My name is Dorothy Farrar, and I'm the founder and main author of this platform.
My passion for health and wellness started at a young age when I became interested in the connection between the food we eat and the way we feel. This fascination led me to study nutrition and dietetics in college, where I learned about the importance of a balanced diet and the impact of various nutrients on the body.