🔬biological chemistry i review

key term - Calcitriol

Definition

Calcitriol is the active form of vitamin D, primarily produced in the kidneys from its precursor, calcidiol. This hormone plays a critical role in maintaining calcium and phosphate homeostasis in the body, which is essential for various biological functions, particularly in bone health and immune system regulation.

5 Must Know Facts For Your Next Test

  1. Calcitriol increases intestinal absorption of calcium and phosphate, helping to ensure adequate levels are available for bone formation and maintenance.
  2. It also promotes the mobilization of calcium from bones into the bloodstream when needed, thus playing a significant role in calcium homeostasis.
  3. Deficiency in calcitriol can lead to conditions such as rickets in children and osteomalacia in adults, highlighting its importance in bone health.
  4. Calcitriol also has effects on the immune system, helping to modulate immune responses and potentially reducing inflammation.
  5. Synthesis of calcitriol is regulated by factors such as sunlight exposure, dietary intake of vitamin D, and hormonal signals from PTH.

Review Questions

  • How does calcitriol contribute to calcium homeostasis in the body?
    • Calcitriol contributes to calcium homeostasis by enhancing the intestinal absorption of calcium and phosphate from food. It also stimulates the release of calcium from bones into the bloodstream when calcium levels are low, ensuring that blood calcium levels remain stable. By coordinating these actions, calcitriol helps to maintain adequate calcium levels for various physiological processes.
  • Discuss the relationship between calcitriol and parathyroid hormone in regulating calcium levels.
    • Calcitriol and parathyroid hormone (PTH) work together to regulate calcium levels in the body. When blood calcium levels drop, PTH is secreted to stimulate the production of calcitriol in the kidneys. Together, they increase intestinal absorption of calcium, promote release of calcium from bones, and reduce renal excretion of calcium, thus raising blood calcium levels effectively.
  • Evaluate the implications of calcitriol deficiency on overall health and development.
    • Calcitriol deficiency can have significant implications on health, leading to diseases such as rickets in children and osteomalacia in adults due to impaired bone mineralization. This deficiency can result from inadequate sunlight exposure or insufficient dietary intake of vitamin D. The consequences extend beyond bone health, as low calcitriol levels may also affect immune function and increase susceptibility to infections or autoimmune diseases, highlighting its critical role in overall health.