key term - Parathyroid hormone

Definition

Parathyroid hormone (PTH) is a crucial hormone produced by the parathyroid glands that regulates calcium levels in the blood and bone metabolism. PTH increases serum calcium levels by stimulating osteoclast activity in bones, enhancing calcium reabsorption in the kidneys, and promoting the activation of vitamin D, which in turn increases intestinal absorption of calcium. Understanding PTH is vital for grasping how drugs can influence bone health and calcium homeostasis.

5 Must Know Facts For Your Next Test

1. PTH is released in response to low blood calcium levels, signaling the body to take action to increase those levels.
2. PTH stimulates osteoclasts, which are cells that break down bone tissue, releasing calcium into the bloodstream.
3. Long-term elevated levels of PTH can lead to bone loss and conditions like osteoporosis.
4. PTH also influences the renal system, enhancing the reabsorption of calcium while promoting the excretion of phosphate.
5. In conjunction with vitamin D, PTH plays a key role in maintaining overall calcium balance and bone health.

Review Questions

• How does parathyroid hormone regulate calcium levels in the body and what are its primary actions?
  • Parathyroid hormone regulates calcium levels by acting on bones, kidneys, and the intestines. It stimulates osteoclast activity in bones to release calcium into the bloodstream, increases renal reabsorption of calcium to prevent its loss through urine, and enhances the activation of vitamin D to promote intestinal absorption of calcium. This multifaceted approach ensures that when blood calcium levels drop, PTH works quickly to restore balance.
• Discuss the relationship between parathyroid hormone and osteoporosis, including how excess levels of PTH can contribute to this condition.
  • Excessive levels of parathyroid hormone can lead to osteoporosis by causing increased bone resorption through enhanced osteoclast activity. This means that if PTH levels remain high for an extended period, it can result in a net loss of bone density as more bone is broken down than is rebuilt. Consequently, individuals with elevated PTH may experience weakened bones that are more susceptible to fractures, illustrating how hormonal balance is critical for maintaining healthy bone metabolism.
• Evaluate the potential therapeutic implications of targeting parathyroid hormone in treating disorders related to bone metabolism.
  • Targeting parathyroid hormone therapeutically could provide significant benefits for treating disorders like osteoporosis. For instance, synthetic analogs of PTH can stimulate new bone formation and increase bone density in patients at risk of fractures. By understanding how PTH functions within the body, researchers can develop more effective drugs that mimic or modulate its actions, potentially reversing bone loss and improving overall skeletal health. This illustrates a promising direction for pharmacological interventions aimed at enhancing calcium homeostasis and treating metabolic bone diseases.

Related terms

Calcitonin: A hormone produced by the thyroid gland that lowers blood calcium levels by inhibiting osteoclast activity and promoting calcium deposition in bones.

Vitamin D:

A fat-soluble vitamin that is essential for calcium absorption in the gut and is activated by PTH to increase serum calcium levels.

Osteoporosis: A condition characterized by weak and brittle bones due to a decrease in bone mass, often linked to imbalances in hormones like PTH.