Calcium metabolism

Academic presentation as junior resident in orthopaedics

1. Calcium Metabolism By Dr kabiru Salisu

2. Outline Introduction Functions of calcium Sources of calcium Daily requirement Absorption Fate of calcium in plasma Role of parathyroid hormone Role of calcitonin Investigation Hypocalcaemia Hypercalcaemia conclusion

3. I ntroduction Calcium metabolism is the process by which body maintain normal and adequate calcium. Ca 2+ is the most abundant cation in the body (1–1.5 kg), 99% being present in bones and teeth The exchangeable pool; 1–2%

4. Calcium regulation can be explain using a rule of 3. Three tissues; (bone, intestine, kidney) Three hormones; (PTH, calcitonin and activated vitamin D3) T hree cell types; ( osteoblasts , osteocytes and osteoclasts ).

5. Functions of calcium Bone growth and remodeling Tooth formation Synaptic transmission Coenzyme function Nerve and neuromuscular transmission Second or third messenger in intracellular signal transduction pathways

6. Sources of calcium The best natural sources include; milk and milk product, egg, fish and bone Cheapest sources include; green leafy vegetable, cereal and millet Other sources; beans, soya-beans, and potato's Drinking water may provide up to 200mg / day of calcium

7. Daily Requirement Daily intake of 400-500mg of ca 2+ has been suggested in adult. Physiological requirement are higher in children, pregnant and lactating mothers

8. Absorption o f calcium From 30% to 80% of ingested calcium is absorbed. Calcium absorption in the small intestine occurs by both active transport and by diffusion. - Active transport predominates in the duodenum and jejunum, and Diffusion in the ileum Ca 2+ absorption is adjusted to body needs.

9. Factors decreasing ca 2+ absorption include; - long-chain saturated fatty acids, i.e. palmitic acid ( forms insoluble calcium soap) - pytic acid - Oxalic acid -Caffeine -Corticosteroid

10. -Fat malabsorption -Liver disease -high phosphate diet

11. Fate of calcium in the plasma The plasma calcium is kept 2.30 and 2.60 mmol /l. - Free or ionised (45%) - Protein bound (45 %) - Complexes with anions – phosphate, sulphate , citrate, lactate (10%);

12. Role of parathyroid hormone PTH is an 84 aa polypeptide. secretion - chief cells The serum level 10–60 pg/ml half-life is 2–4mn Serum level control via –ve feed

13. Action PTH maintains the plasma ionized calcium level via; I- Osteolysis by increasing the numbers and activity of osteoclasts as well as transport. II- It increases proximal renal tubular reabsorption of calcium III- increase activity of 1 α hydroxylase

14. Calcitonin 32 aa polypeptide Secretion:- parafollicular or C cells of the thyroid gland

15. Action It diminishes osteolytic activity Inhibition of jejunal absorption of calcium Inhibition of tubular reabsorption and promotion of urinary excretion calcium Inhibition 1 α - hydroxylase activity

16. Investigation Sample taking, patient should fast for at least 8hr to prevent heamo -concentration of calcium No use of tourniquet ca2+/albumin are requested

17. Calcium correction Corrected ca 2+ ( mmol /l)= (Ca) + 0.02 (40 - albumin) Corrected calcium (mg/ dL ) = Ca (mg/ dL ) + 0.8 (4.0 - serum albumin [g/ dL ]),

18. hypocalcemia A corrected serum calcium concentration < 2.2 mmol /L or an ionized calcium concentration < 1.2 mmol /L

19. causes Vitamin D deficiency or target organ resistance; Dietary deficiency or malabsorption ; liver disease Renal failure Anticonvulsants PTH deficiency or target organ resistance; Hyperphosphataemia Loss of calcium from the circulation: excessive chelation.

20. Features of hypocalcaemia - Mild hypocalcemia ; may be asymptomatic or accompanied by nonspecific central nervous system (CNS) signs - Chronic hypocalcaemia; may present with mild diffuse brain disease mimicking depression, dementia, or psychosis. cataracts and calcification of the basal ganglia

21. Severe hypocalcaemia < 0.75 mmol /L ; Tetany develops, esp. when an associated alkalosis. Tetany is characterized by paresthesias (particularly around the mouth, lips, and tongue) and muscle spasms, particularly of the hands, feet, and face

22. Severe hypocalcemia can also occasionally cause cardiac arrhythmias and heart block. An ECG typically shows a prolonged QT interval.. Latent neuromuscular instability can be elicited by; Chvostek's sign Trousseau's sign

23. Treatment -vitamin D3 0.5-2µg/ day and -Elemental calcium 1-2g/ day individed doses -Diuretics IV 10% calcium Gluconate

24. hypercalcaemia A corrected serum calcium concentration > 2.6 mmol /L. I onized calcium concentration > 1.3 mm ol /L). Hypercalcemia is common and dangerous in the elderly.

25. causes Parathyroid hormone related: primary or secondary hyperparathyroidism ectopic PTH secretion. Vitamin D related: vitamin D toxicity; granulomatous dx Excess vit . D3 production. Malignancy: increased osteoclastic activity due to bone destruction by primary or metastatic tumour . Drugs;- thiazide diuretics; lithium; vitamin A and analogues. Endocrine disorders: thyrotoxicosis ; adrenocortical insufficiency.

26. features Mild hypercalcemia usually asymptomatic Affected patients may have hypertension, muscular weakness and irritability, mild GI disturbances, renal colic, bone cysts, impaired renal function ( polyuria ), and decreased bone mass.

27. Hypercalciuria and nephrolithiasis may occur . Bone lesion; subperiosteal bone resorption of the hands and a salt-and-pepper-like appearance of the skull can be observed radiologically . Patients with primary hyperparathyroidism usually lose cortical bone mass in the appendicular skeleton

28. Severe hypercalcaemia Severe dehydration;- vomiting, anorexia, polyurea . When the serum calcium is > 3 mmol /L mental confusion can occur. concentration may increase with dehydration, resulting in coma and death.

29. treatment Depend on; Cause Rapidity of calcium raise Serum calcium level

30. - Rehydration - Diuretics - Calcitonin - Prednisalone - NSAID - heamodialysis

31. Other disease associated with defect in calcium and it metabolism include; Rickets & Osteomalacia osteoporosis Renal osteodystrophy

32. Conclusion Calcium being most abundant cation in the body is essential for life because of it role in skeletal system and several metabolic activity

33. Thank you for listening

34. They Need Enough Calcium