💊intro to pharmacology review

key term - Calcitriol

Definition

Calcitriol is the active form of vitamin D in the body, primarily responsible for regulating calcium and phosphate levels, which are crucial for maintaining healthy bones. It is produced in the kidneys from its precursor, calcidiol, and plays a key role in bone metabolism by enhancing intestinal absorption of calcium and phosphate, thus contributing to bone health and homeostasis.

5 Must Know Facts For Your Next Test

  1. Calcitriol promotes the intestinal absorption of dietary calcium and phosphate, which are essential for bone mineralization.
  2. It plays a critical role in bone remodeling by influencing the activity of osteoblasts and osteoclasts, the cells responsible for building and resorbing bone tissue.
  3. Deficiency in calcitriol can lead to disorders such as rickets in children and osteomalacia in adults, both of which result in weakened bones.
  4. Calcitriol also helps regulate the reabsorption of calcium in the kidneys, reducing calcium loss through urine.
  5. The production of calcitriol is stimulated by parathyroid hormone when blood calcium levels are low, ensuring a balance between calcium intake and maintenance.

Review Questions

  • How does calcitriol contribute to calcium homeostasis and what would happen if its levels are insufficient?
    • Calcitriol is essential for calcium homeostasis because it increases the absorption of calcium from the gut and minimizes renal excretion. If calcitriol levels are insufficient, it can lead to lower calcium absorption, resulting in increased parathyroid hormone secretion to compensate. This imbalance may lead to conditions like rickets or osteomalacia due to inadequate mineralization of bone.
  • Evaluate the role of calcitriol in bone metabolism compared to that of parathyroid hormone.
    • Calcitriol and parathyroid hormone work synergistically to regulate bone metabolism. While calcitriol enhances the absorption of calcium and phosphate from the intestine and promotes bone mineralization, parathyroid hormone primarily works to increase blood calcium levels by stimulating bone resorption and renal reabsorption of calcium. Together, they ensure that calcium levels remain stable, balancing bone formation and resorption.
  • Discuss how alterations in calcitriol synthesis can affect overall skeletal health and contribute to conditions like osteoporosis.
    • Alterations in calcitriol synthesis can significantly impact skeletal health by disrupting calcium balance. Low levels of calcitriol result in decreased intestinal absorption of calcium, leading to hypocalcemia. Over time, this deficiency can trigger increased bone resorption as the body attempts to maintain serum calcium levels, contributing to osteoporosis. Adequate calcitriol is necessary for maintaining bone density and preventing fragility fractures.