1. Basic Orthopaedic Tutorial
Blood Calcium, Phosphorus,
and Magnesium

2.  Regulator: PTH ; 1,25 (OH)2 vit D ; Calcitonin
 The metabolically active tissues :
1. Bones
2. Kidneys
3. Intestine

3.  Normal level: 9.0 – 10.4 mg / 100 mL

1%
99%

4.  Absorption
 Active transport – duodenum
▪ Require ATP & regulated by vit D
 Passive diffusion – jejunum
 Reabsorption
 98% ca reabsobed in kidney

5. Calcium Diet
 Dietary requirement
 Children : 600 mg/ day
 Adolescent & young adult : 1300 mg / day
 Adult : 750 mg / day
 Pregnant women : 1500 mg / day
 Lactating women : 2000 mg /day
 Post menopausal women : 1500 mg / day
 Patients w/ a long bone fracture: 1500 mg / day

6. Functions of Calcium
 Controls internal regulation of function of all
cells
 Regulates cell membrane permeability, nerve
excitability, muscle contraction, and gland
secretion
 Regulates synthetic and secretory functions of
PTH and thyroid C cells (for calcitonin)
 Control adhesiveness between cells
 Controls the hardness and rigidity of bones
and teeth through hydroxyapatite

7. Calcium homeostasis

9. Disease Etiology
Hypercalcemia
HyperPTH PTH overproduction -adenoma
Familial syndromes PTH overproduction - Multiple
endocrine neoplasia type I and II
Hypocalcemia
HypoPTH PTH underproduction – idiopathic,
iatrogenic
Pseudohypoparathyroidism / PTH receptor abnormality
Albright syndrome
Renal Osteodystrophy CRF – Pi excretion ↓
Rickets (Osteomalacia) Nutritional, vit D dependent, vit D
resistant

11. Phosphate (Pi)
 Normal level : 2.8 – 4.0 mg/dL
 85%  bone
 Reabsorption  kidney (renal tubular) 70 – 90%
 Stimulated by 1,25 (OH)2 D
 Inhibited by PTH
 Daily requirements: 1000 – 1500 mg/ day
 Together with Ca – normal bone metabolism

12. Phosphate homeostasis

13.  Small role in bone homeostasis
 Required for parathyroid hormone secretion.
 Efficient peripheral action of PTH
◦ cofactor