1. DISORDERS OF CALCIUM AND PHOSPHATE
METABOLISM

2. INTRODUCTION
Calcium and phosphorus homeostasis is auto-regulated by Vitamin D.
This is characterized by;
Increasing intestinal absorption of calcium and phosphorus, mobilizing calcium and
phosphorus from bone and stimulating Ca reabsorption and phosphorus excretion in
the kidney
In the kidney, 1,25(OH)2D inhibits renal 1α-hydroxylase and stimulates 24-hydroxylase
(which degrades vitamin d), thereby reducing production and increasing catabolism of
1,25(OH)2D

3. DISORDERS
Chronic inflammatory conditions of the kidneys, heart, GI tract: negatively associated
with c-reactive protein with hemoabdomen abnormalities in cellular function as well as
cytokine levels
Inflamatory bowel disease (IBD) such as crohn's disease and ulcerative colitis cause severe
tummy pain and diarrhoea
Infections in humans such as mycobacteria, influenza, tuberculosis and hiv; and spirocerca
lupi infections. low levels of vitamin d and the immune response to this infection
(mycobacterial infections, staphylococcus pneumonia)
Neoplasia: vitamin d metabolism and its effect on cancer development and metabolism.
Hypovitaminosis of 25 (OH)D concentrations have been associated with an increased
incidence of cancer

4. Biosynthesis and Regulation of Calcitriol

5. MAJOR MEDIATORS OF CALCIUM AND PHOSPHATE BALANCE
Parathyroid Hormone (PTH)
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
Role of Calcitriol
 Stimulates GI absorption of both calcium and
phosphate
 Stimulates renal reabsorption of both calcium
and phosphate
 Stimulates bone resorption
Calcitriol (active form of vitamin D3)

6. Calcium Biochemical Metabolism

7. Overview of Calcium Biochemical Homeostasis

8.  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-incase of Hyperparathyroidism
 Malignancy incase of Osteolytic metastases and
PTHrP secreting tumor
 Increased bone turnover; Pagets disease of bone
Hyperthyroidism
Decreased Bone Mineralization Elevated
• PTH and Aluminum toxicity
Causes of Hypercalcemia
Decreased Urinary Excretion
• i.e Thiazide diuretics, Elevated, calcitriol
Elevated PTH

9. Overview of phosphorous Biochemical Homeostasis

10.  Increased GI Intake
 Fleets Phospho-Soda
 Cell Lysis
 Rhabdomyolysis
 Tumor lysis syndrome
 Decreased Urinary Excretion
 Renal Failure
 Low PTH (hypoparathyroidism)
 s/p thyroidectomy
 s/p I131 treatment for Graves disease of
thyroid cancer
 Autoimmune hypoparathyroidism
Causes of Hyperphosphatemia

11. Overview of Calcium-Phosphate Regulation