Calcitriol

Definition

Calcitriol is the active form of vitamin D, crucial for maintaining calcium and phosphate balance in the body. It is produced in the kidneys from its precursor, calcidiol, and plays a significant role in regulating mineral metabolism and promoting the absorption of calcium from the intestines, which is essential for bone health and muscle function.

5 Must Know Facts For Your Next Test

1. Calcitriol helps increase the intestinal absorption of dietary calcium and phosphate, which are vital for healthy bone formation.
2. In renal nutrition, insufficient production of calcitriol can lead to issues such as bone disease and imbalances in calcium and phosphorus levels.
3. The synthesis of calcitriol is stimulated by parathyroid hormone (PTH), especially when serum calcium levels are low.
4. Calcitriol also has important roles beyond bone health, influencing immune function and cell growth regulation.
5. Patients with chronic kidney disease may experience a reduction in calcitriol production, necessitating supplementation to prevent complications.

Review Questions

• How does calcitriol influence calcium and phosphate balance in patients with kidney issues?
  • Calcitriol plays a critical role in managing calcium and phosphate levels, particularly in patients with kidney issues. In healthy individuals, calcitriol promotes the absorption of these minerals from the intestine. However, when kidney function declines, there is a decrease in calcitriol production, leading to potential deficiencies that can result in imbalances and contribute to conditions such as renal osteodystrophy.
• Discuss the relationship between calcitriol and parathyroid hormone (PTH) in maintaining mineral homeostasis.
  • Calcitriol and parathyroid hormone (PTH) work together to maintain mineral homeostasis. When blood calcium levels drop, PTH is released from the parathyroid glands, stimulating the kidneys to convert more calcidiol to calcitriol. This active form of vitamin D then enhances intestinal absorption of calcium and phosphate while also promoting bone resorption when necessary. This coordinated response helps restore normal serum calcium levels.
• Evaluate the consequences of impaired calcitriol synthesis in patients with chronic kidney disease and propose potential management strategies.
  • Impaired calcitriol synthesis in patients with chronic kidney disease can lead to serious consequences like secondary hyperparathyroidism, renal osteodystrophy, and increased risk of fractures due to weakened bones. Management strategies may include administering active forms of vitamin D such as calcitriol or its analogs to improve mineral balance. Additionally, dietary modifications to increase calcium and phosphorus intake, along with monitoring and potentially adjusting phosphate binders, can also be essential in mitigating these effects.

Related terms

Vitamin D: A fat-soluble vitamin that is important for maintaining bone health by facilitating calcium absorption in the gut.

Parathyroid Hormone (PTH): A hormone released by the parathyroid glands that helps regulate calcium levels in the blood, often working in conjunction with calcitriol.

Phosphate: An essential mineral that works with calcium to build and maintain bones and teeth, also playing a role in energy production.