Endocrinology: Calcium and Phosphate Regulation

Endocrinology: Calcium and Phosphate Regulation

Importance of Calcium and Phosphate

• Calcium is essential for muscle contraction and nerve conduction
• Phosphate is crucial for biochemical processes and energy production
• Regulation of calcium and phosphate levels is necessary for proper bodily functions

Hormones Involved

• Vitamin D (active form: calcitriol)
• Parathyroid hormone
• Calcitonin

Parathyroid Hormone

• Released when plasma calcium levels decrease
• Targets:
  • Bone: stimulates breakdown, releasing calcium and phosphate into plasma
  • Kidneys: activates enzyme 1-alpha hydroxylase, converting vitamin D to calcitriol
• Increases calcium and phosphate levels in plasma

Calcitriol (Active Form of Vitamin D)

• Converts vitamin D to active form
• Targets:
  • Bone: stimulates breakdown, releasing calcium and phosphate into plasma
  • Kidneys: stimulates reabsorption of calcium in proximal convoluted tubules
  • GI Tract: increases calcium and phosphate absorption
• Negatively feedbacks on parathyroid gland, reducing parathyroid hormone production

Calcitonin

• Released when plasma calcium levels increase
• Decreases plasma calcium levels
• Has a lesser role in calcium regulation compared to parathyroid hormone

Bone Structure and Function

• Composed of osteoblasts (build bone) and osteoclasts (break down bone)
• Osteoblasts have parathyroid hormone receptors, which induce:
  • Proliferation
  • RANK ligand expression
  • Inhibition of osteoprotegerin production
• RANK ligand binding to RANK receptors on pre-osteoclasts induces:
  • Proliferation
  • Differentiation into active osteoclasts
• Macrophage Colony Stimulating Factor (M-CSF) also stimulates osteoclast proliferation and differentiation

Calcium and Phosphate Regulation

Importance of Calcium and Phosphate

• Calcium is essential for muscle contraction and nerve conduction
• Phosphate is crucial for biochemical processes and energy production
• Regulation of calcium and phosphate levels is necessary for proper bodily functions

Hormones Involved in Calcium and Phosphate Regulation

• Vitamin D (active form: calcitriol)
• Parathyroid hormone
• Calcitonin

Parathyroid Hormone

• Released when plasma calcium levels decrease
• Stimulates bone breakdown, releasing calcium and phosphate into plasma
• Activates enzyme 1-alpha hydroxylase, converting vitamin D to calcitriol in kidneys
• Increases calcium and phosphate levels in plasma

Calcitriol (Active Form of Vitamin D)

• Converts vitamin D to active form
• Stimulates bone breakdown, releasing calcium and phosphate into plasma
• Stimulates calcium reabsorption in kidney proximal convoluted tubules
• Increases calcium and phosphate absorption in GI tract
• Negatively feedbacks on parathyroid gland, reducing parathyroid hormone production

Calcitonin

• Released when plasma calcium levels increase
• Decreases plasma calcium levels

Bone Structure and Function

• Composed of osteoblasts (build bone) and osteoclasts (break down bone)
• Osteoblasts have parathyroid hormone receptors, inducing:
  • Proliferation
  • RANK ligand expression
  • Inhibition of osteoprotegerin production
• RANK ligand binding to RANK receptors on pre-osteoclasts induces:
  • Proliferation
  • Differentiation into active osteoclasts
• Macrophage Colony Stimulating Factor (M-CSF) stimulates osteoclast proliferation and differentiation

Learn about the importance of calcium and phosphate in the body, and how they are regulated by hormones like vitamin D, parathyroid hormone, and calcitonin.