Parathyroid Hormone PTH and Its Role in Calcium Homeostasis

Normal PTH Levels

The parathyroid hormone is a secretion of four parathyroid glands present in a human body. These glands are a vital part of the endocrine system, they are negligibly small, i.e., around the size of a grain of wheat or rice. They are situated in the neck behind the thyroid gland. These glands constantly monitor and thus regulate the levels of calcium in the blood. The regulation of calcium levels helps to control our bone density. The depleted bone mass is restored with the constant and vigilant supply of calcium. The process is controlled with the help of parathyroid hormone (PTH). What is parathyroid hormone? It is a hormone secreted by the parathyroid glands that helps in the regulation of blood calcium level. A lack of the hormone will imbalance the level of calcium, the lack of it will lead to brittleness of the bones, and too much of it can lead to the formation of kidney stones. The normal PTH levels are needed for healthy well-being. 

[Image Will be Uploaded Soon]

Functions of the Parathyroid Hormones

The parathyroid hormone, also called as parathormone, serves the primary function of regulating the levels of calcium in the blood to control the density of bones. It has to maintain a strict range between 9.0 to 10.1. It also helps in increasing the production of activated vitamin D; thus, the absorption of calcium in the intestine is consequently increased. Besides, in the process of breakdown of calcium from the bones, the hormone helps the reabsorption of calcium from the proximal tubule, distal tubule and renal collecting ducts. Another important parathyroid hormone’s function is the regulation of phosphate. PTH also helps in reducing the reabsorption of phosphate from the proximal tubule of the kidneys and excreting the remaining phosphate through the process of urination. On the other hand, it also uptakes phosphate from bones and intestines into the bloodstream. In the intestines, it regulates the absorption of both calcium and phosphate by regulating activated vitamin D. 

Hyperparathyroidism

Hyperparathyroidism is the condition in which there is an abnormal increase in the PTH levels in the blood of the affected person. It is caused by a dysfunction either within or outside the glands. The internal dysfunction is called primary hyperparathyroidism, and the external dysfunction is called secondary hyperparathyroidism. 

(1) Primary Hyperparathyroidism- In this form of condition, there is an abnormality inside or adjacent to the parathyroid glands; e.g., a cancerous or non-cancerous tumorous growth on the gland, or hyperplasia, i.e., enlargement of at least two of those glands. The cause of primary hyperparathyroidism may be through inheritance, as well. 

(2) Secondary Hyperparathyroidism- It is a problem that, too, leads to the overproduction of the parathyroid hormones; however, the problem is not directly linked with any physical abnormality of the parathyroid glands. The overproduction of PTH can have some devastating effects on the affected person. The major risk factor is that there can be formations of kidney stones due to heavy and prolonged calcification. This can lead to excruciating pain in the kidney, particularly during urination. 

Hypoparathyroidism

Hypoparathyroidism is characterised by lower than normal levels of the PTH in the blood of the affected person. It is caused by the decreased function of the parathyroid glands. Due to hypothyroidism, the levels of calcium in the blood depletes; it can lead to tetany; i.e., cramping or involuntary twitching of the muscles. Along with depletion of calcium, the condition also causes higher than usual levels of phosphate. There are some signs and symptoms that can help diagnosis of hypoparathyroidism. These signs are cramps and aches in the muscles of the legs, face and stomach; burning sensation in the toes, lips and fingertips; lethargy; painful menstruation; dry and uneven skin; brittleness of nails; and patchy hair loss. With the depleted calcium from the body, the bones become fragile and may crack or break easily. Also, it can result in stunted growth and delayed mental development in children and calcium deposition in the brain. Hypoparathyroidism can be caused by neck surgery, heredity, autoimmune disease, repeated radiation on the neck for cancer treatment, low levels of magnesium in your blood.

Treatment

For hyperparathyroidism, anti-thyroid medicines and administration of radioactive iodine are the options. Surgical removal of parathyroid adenoma, i.e., non-cancerous tumours, and removal of the cancerous tumour will resolve the problem. For hypoparathyroidism, administration of intravenous calcium gluconate can help someone restore the right amount of calcium in the body. Injection of recombinant human parathyroid hormone can be a lifelong treatment with the supplement of calcium for someone with an irreversible condition.