Parathormone
Parathyroid hormone (PTH), also referred to as parathormone, is a vital hormone involved in the regulation of calcium and phosphorus levels in the body. Produced by the parathyroid glands, which are four small glands located behind the thyroid gland in the neck, PTH plays a central role in maintaining mineral homeostasis and ensuring the proper functioning of numerous physiological processes.
The discovery of parathyroid hormone dates back to the early 20th century when researchers were investigating the role of the parathyroid glands in calcium metabolism. In 1925, Eugene F. DuBois and colleagues identified a substance secreted by the parathyroid glands that was responsible for raising blood calcium levels. This substance was later named parathyroid hormone.
The primary function of parathyroid hormone is to regulate calcium levels in the blood. Calcium is essential for various cellular processes, including muscle contraction, nerve transmission, and bone formation. PTH achieves calcium homeostasis through several mechanisms:
Stimulation of Bone Resorption: PTH stimulates osteoclasts, specialized cells responsible for breaking down bone tissue. By promoting bone resorption, PTH releases calcium stored in bones into the bloodstream, increasing blood calcium levels.
Enhancement of Calcium Reabsorption in the Kidneys: PTH acts on the kidneys to increase the reabsorption of calcium from the urine back into the bloodstream. This reduces calcium loss through urine excretion, helping to conserve calcium in the body.
Stimulation of Vitamin D Activation: PTH stimulates the kidneys to produce an active form of vitamin D called calcitriol. Calcitriol enhances calcium absorption in the intestines, further increasing blood calcium levels.
In addition to its effects on calcium, parathyroid hormone also regulates phosphorus levels in the blood. PTH decreases blood phosphate levels by promoting phosphate excretion in the urine, helping to maintain an appropriate balance between calcium and phosphate in the body.
Parathyroid hormone secretion is tightly regulated by calcium levels in the blood through a negative feedback mechanism. When blood calcium levels are low, the parathyroid glands increase PTH secretion, leading to the actions described above that raise blood calcium levels. Conversely, when blood calcium levels are elevated, PTH secretion is inhibited, helping to prevent hypercalcemia (excessive calcium levels).
Dysregulation of parathyroid hormone secretion can lead to disorders such as hyperparathyroidism and hypoparathyroidism. Hyperparathyroidism is characterized by excessive PTH production, resulting in elevated blood calcium levels, which can lead to symptoms such as bone pain, kidney stones, and gastrointestinal disturbances. Hypoparathyroidism, on the other hand, is characterized by insufficient PTH production, leading to low blood calcium levels, which can cause muscle spasms, seizures, and cardiac abnormalities.
In conclusion, parathyroid hormone plays a critical role in maintaining calcium and phosphorus homeostasis in the body. Through its actions on bone, kidneys, and vitamin D metabolism, PTH ensures that blood calcium levels are tightly regulated, supporting numerous physiological processes essential for overall health and wellbeing.
parathormone function:
Parathyroid hormone (PTH), also known as parathormone, plays several important roles in the body’s regulation of calcium and phosphorus levels:
Calcium Regulation: PTH increases blood calcium levels by stimulating the release of calcium from bones (bone resorption), reducing calcium loss in urine, and increasing calcium absorption in the intestines. These actions help maintain the concentration of calcium in the blood within a narrow range, which is essential for various physiological processes such as muscle contraction, nerve function, and blood clotting.
Phosphate Regulation: PTH decreases blood phosphate levels by inhibiting phosphate reabsorption in the kidneys, leading to increased phosphate excretion in urine. Lowering phosphate levels helps to counterbalance the effects of increased calcium levels, as high calcium and phosphate levels can lead to the formation of calcium-phosphate crystals in tissues.
Vitamin D Activation:Â PTHÂ stimulates the kidneys to convert inactive vitamin D (calcidiol) into its active form (calcitriol). Active vitamin D enhances calcium absorption in the intestines, further contributing to increased blood calcium levels.
Overall, parathyroid hormone functions to maintain calcium and phosphate homeostasis in the body, ensuring that these minerals are available in appropriate amounts for vital physiological processes. Dysregulation of PTH secretion can lead to disorders such as hyperparathyroidism (excessive PTH production) or hypoparathyroidism (insufficient PTH production), which can disrupt calcium and phosphate balance and result in various health problems, including bone disorders, kidney stones, and neurological symptoms.