Parathyroid hormone

Definition

Parathyroid hormone (PTH) is a key regulator of calcium and phosphate metabolism in the body, secreted by the parathyroid glands. It plays a crucial role in maintaining serum calcium levels by promoting calcium release from bones, increasing calcium reabsorption in the kidneys, and enhancing intestinal absorption of calcium through its effects on vitamin D. Understanding PTH is essential for grasping how disorders of the parathyroid glands can lead to various health issues, particularly concerning bone health and mineral balance.

5 Must Know Facts For Your Next Test

1. Parathyroid hormone is secreted in response to low serum calcium levels and works to increase those levels through several mechanisms.
2. PTH stimulates osteoclast activity in bones, which leads to the release of calcium into the bloodstream.
3. In the kidneys, parathyroid hormone increases the reabsorption of calcium while promoting the excretion of phosphate.
4. Long-term elevated levels of PTH can lead to bone demineralization, making bones weaker and more susceptible to fractures.
5. PTH also activates vitamin D, which further enhances calcium absorption from dietary sources in the intestines.

Review Questions

• How does parathyroid hormone contribute to the regulation of calcium levels in the body?
  • Parathyroid hormone helps regulate calcium levels by acting on bones, kidneys, and intestines. When blood calcium levels drop, PTH is released, stimulating osteoclasts to break down bone tissue and release calcium into the bloodstream. It also promotes renal reabsorption of calcium and increases intestinal absorption of calcium through its activation of vitamin D. Together, these actions help restore normal calcium levels in the body.
• Discuss the pathophysiology and potential complications associated with hyperparathyroidism.
  • Hyperparathyroidism occurs when there is an overproduction of parathyroid hormone, often due to an adenoma or hyperplasia of the parathyroid glands. This excess PTH leads to increased serum calcium levels, resulting in symptoms like kidney stones, osteoporosis, and abdominal pain. Over time, chronic elevated calcium levels can cause significant damage to organs such as the kidneys and can increase the risk of cardiovascular disease due to calcification of tissues.
• Evaluate the role of parathyroid hormone in maintaining mineral homeostasis, particularly concerning bone health and dietary intake.
  • Parathyroid hormone plays a critical role in maintaining mineral homeostasis by balancing calcium and phosphate levels through its actions on bones, kidneys, and intestines. By stimulating osteoclasts to release calcium from bones and increasing renal reabsorption while promoting vitamin D activation for better dietary absorption, PTH ensures that adequate calcium is available for essential physiological functions. This balance is vital for bone health; too much PTH can lead to weakened bones while too little can result in insufficient mineralization.

Related terms

Calcitonin: A hormone produced by the thyroid gland that lowers blood calcium levels by inhibiting bone resorption and promoting calcium excretion in the kidneys.

Hyperparathyroidism: A condition characterized by excessive secretion of parathyroid hormone, leading to elevated levels of calcium in the blood, which can cause various symptoms and complications.

Vitamin D: A fat-soluble vitamin that enhances intestinal absorption of calcium and phosphate, working synergistically with parathyroid hormone to regulate mineral balance.