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.
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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.
FAQs on Parathyroid Hormone
1. What is the primary function of Parathyroid Hormone (PTH) in the body?
The primary function of Parathyroid Hormone (PTH), a peptide hormone secreted by the four parathyroid glands, is to regulate calcium levels in the blood. PTH is a hypercalcemic hormone, meaning it works to increase blood calcium concentrations when they fall too low, ensuring the proper functioning of the nervous and muscular systems.
2. How does Parathyroid Hormone (PTH) increase blood calcium levels?
Parathyroid Hormone (PTH) increases blood calcium levels through a coordinated action on three main target organs:
- Bones: PTH stimulates a process called bone resorption, where it promotes the activity of osteoclasts. These cells break down bone matrix, releasing stored calcium and phosphate into the bloodstream.
- Kidneys: It enhances the reabsorption of calcium from the renal tubules, preventing its loss in urine. It also stimulates the kidneys to convert inactive Vitamin D to its active form, calcitriol.
- Intestines: By activating Vitamin D, PTH indirectly increases the efficiency of calcium absorption from digested food in the intestines.
3. What is hyperparathyroidism and what are its main symptoms?
Hyperparathyroidism is a disorder caused by the overproduction of Parathyroid Hormone (PTH). This leads to abnormally high levels of calcium in the blood (hypercalcemia). The main symptoms are a result of this excess calcium and include weakening of bones (osteoporosis), formation of kidney stones, bone pain, muscle weakness, and fatigue.
4. What happens if the Parathyroid Hormone (PTH) level is too low?
If PTH levels are too low, a condition known as hypoparathyroidism occurs. This deficiency leads to a drop in blood calcium levels (hypocalcemia). The primary consequence is increased neuromuscular excitability, which can cause symptoms like muscle twitching, cramps, numbness, and in severe cases, a condition called tetany, characterized by sustained, involuntary muscle contractions.
5. How do Parathyroid Hormone (PTH) and Calcitonin work together to maintain calcium balance?
Parathyroid Hormone (PTH) and Calcitonin are antagonistic hormones that have opposite effects on blood calcium levels, creating a precise balance. While PTH is a hypercalcemic hormone that raises blood calcium, Calcitonin (secreted by the thyroid gland) is a hypocalcemic hormone that lowers it. When blood calcium is high, Calcitonin is released to promote calcium deposition in bones. When it's low, PTH is released to pull calcium from bones, ensuring a stable level or homeostasis.
6. What is the feedback mechanism that controls the secretion of Parathyroid Hormone?
The secretion of Parathyroid Hormone (PTH) is controlled by a classic negative feedback loop based on blood calcium concentration. When circulating calcium levels fall below the normal range, it is detected by the parathyroid glands, which are then stimulated to secrete PTH. As PTH raises blood calcium levels, the increased calcium concentration then feeds back to the parathyroid glands, inhibiting further PTH secretion. This self-regulating system ensures calcium homeostasis.
7. Why is Vitamin D essential for the function of Parathyroid Hormone?
Vitamin D is essential because PTH itself cannot directly facilitate calcium absorption from the gut. Instead, one of PTH's key actions is to stimulate the kidneys to convert inactive Vitamin D into its active form, calcitriol. It is this active calcitriol that is directly responsible for promoting the absorption of calcium from the small intestine. Therefore, without adequate Vitamin D, the body's ability to acquire calcium from diet is severely impaired, making PTH's job of regulating blood calcium much less effective.
8. What is hypocalcemic tetany and how is it related to the parathyroid gland?
Hypocalcemic tetany is a serious medical condition characterized by involuntary muscle spasms and contractions. It is directly related to the parathyroid gland because it is caused by a severe deficiency of blood calcium (hypocalcemia). This condition typically arises from hypoparathyroidism, where the parathyroid glands fail to secrete enough PTH. Without sufficient PTH, blood calcium levels drop, leading to a state of high neuromuscular excitability and causing the uncontrolled muscle activity seen in tetany.
