Calcium disorders Flashcards
ROle of calcium
- bone formation
- muscle contraction
- Signalling
3 sources for calcium (where body gets ca)
- Absorption via S. Int w/ Vit D
- Resorption via bone
- Reabsorbtion via kidneys
a inc/dec in [2x ions] excites nerve/muscle cells
inc Ca = excite nerves
low K = excite nerves = weakness
(Hi K = cardiac arrest)
total plasma calcium =
ionised Ca + Ca bound/complex w/ Alb
*equ. need to be adjusted in hypocalcemia
ROle of phosphate
- bone formation
- component for dNTP
- energy cycles
What is Rhabdomyolysis
major injury & muscle damage = inc PO4 bind to Ca2+ => hypocalcemia
hormones involved in regulating Ca & role
- PTH: increase Ca & dec PO4 in blood
- Vit D: inc Ca & PO4 in blood
- Calcitonin: reduce Ca in blood
which plasma Ca is biologically active?
Ca2+ (ionised Ca)
Most of body’s phosphate, calcium and magnesium are in
skeletal
How can blood pH affect ionised Ca?
- H+ competes w/ Ca2+ for binding w/ Alb (-ve) => Free Ca2+
- acidosis = Hi H+ = More Ca2+ (ionised form)
- Alkalosis = Lo H+ = Less Ca2+
relationship of PO4 & Ca
inverse proprtional
inc. PO4 = dec Ca2+
Normal calcium metabolism depends on (5)
- Parathyroid (PTH) function
- Renal function (creatinine)
- Intestinal Function
- Adequate supply of vitamin D - made in kidneys
- Adequate supply of calcium
Which of the following hormones is often associated with malignancy?
PTHrP
how is PTH release stimulated
- hypocalcemia
- hyperphosphatemia
- hypermagnesiemia
Why children are having high ALP?
Because they have high osteoblast
how active vit D is formed
- In skin, UV irradiation converts 7-dehydroxycholesterol => cholecalciferol (Vit. D)
- => 25-dihydroxycholecalciferol in liver
- => active Vit D = 1,25 (OH)2 vit D3 (calcitriol) in the kidneys by 1 alpha hydroxylase
Rickets vs Osteomalacia
- Poor bone mineralization due to VitD3 deficiency or calcium
=> Rickets: soft bones in CHILDREN OR
OR => Osteomalacia: soft bones in ADULTS
causes of Vit Ddeficiency
- Hi altitudes = low exposure to sunlight
- Malabsorption of food in GIT
- Renal disease
- hypothyroidism
effects of hypercalcemia from excess vit D
- Calcium deposition in soft tissues
- Renal damage
- Cardiac damage
Action of PTH & Vit D in stimulating osteoclast activity
- PTH stimulates 1-a-hydroxylase to convert inactive Vit D into (1,25(OH)2-VitD3)
- => osteoblast ligand (RANKL) expressed
- osteoclast activity inc = bone resorption = inc Ca in blood
role of Calcitonin
- Lowers plasma phosphate
- Lowers plasma calcium
- Inhibits actions of PTH
- Inhibits actions of calcitriol
Causes of hypOcalcaemia
- Hepatobiliary diseases
- Magnesuim deficiency
- Vit D deficiency
- Hypoparathyroidism
Name the condition: lack of renal response to PTH due to kidney resistance to PTH.
Pseudohypoparathyroidism
Causes of hypERcalcaemia
- PTHrp
- Hyperparathyroidism
- Multiple myeloma
- High albumin
- Vit D intoxication
