Disorders of Calcium and Phosphate Metabolism

Disorders of Calcium and Phosphate Metabolism

Outline
* Review of calcium and phosphate metabolism
* Abnormalities of calcium balance
* Abnormalities of phosphate balance
* Example cases

Major Mediators of Calcium and Phosphate Balance
* Parathyroid hormone (PTH)
* Calcitriol (active form of vitamin D3)

Role of PTH
* Stimulates renal reabsorption of calcium
* Inhibits renal reabsorption of phosphate
* Stimulates bone resorption
* Inhibits bone formation and mineralization
* Stimulates synthesis of calcitriol
Net effect of PTH
Regulation of PTH
Role of Calcitriol
* Stimulates GI absorption of both calcium and phosphate
* Stimulates renal reabsorption of both calcium and phosphate
* Stimulates bone resorption

Net effect of calcitriol
Regulation of Calcitriol
Overview of Calcium-Phosphate Regulation
Different Forms of Calcium
Calcium in the plasma:
Overview of Biochemical Homeostasis
Overview of Calcium Balance
Etiologies of Hypercalcemia
Increased GI Absorption
Milk-alkali syndrome
Elevated calcitriol
Vitamin D excess
Excessive dietary intake
Granuomatous diseases
Elevated PTH
Hypophosphatemia

Increased Loss From Bone
Increased net bone resorption
Elevated PTH
Hyperparathyroidism
Malignancy
Osteolytic metastases
PTHrP secreting tumor
Increased bone turnover
Paget’s disease of bone
Hyperthyroidism
Decreased Bone Mineralization
Elevated PTH
Aluminum toxicity
Decreased Urinary Excretion
Thiazide diuretics
Elevated calcitriol
Elevated PTH
Etiologies of Hypocalcemia
Decreased GI Absorption
Decreased Bone Resorption/Increased Mineralization
Increased Urinary Excretion
Overview of Phosphate Balance
Etiologies of Hyperphosphatemia
Increased GI Intake
Decreased Urinary Excretion
Cell Lysis
Etiologies of Hypophosphatemia
Decreased GI Absorption
Decreased Bone Resorption / Increased Bone Mineralization
Increased Urinary Excretion
Internal Redistribution (due to acute stimulation of glycolysis)
4 Case stuides

Disorders of Calcium and Phosphate Metabolism.ppt