Calcium Flashcards
Threat to calcium homeostasis?
- gut
- kidney
- skeleton
- steatorrhoea
- renal failure
- bony metastases
Threat to calcium homeostasis?
- Parathyroid
adenoma
damage due to thyroid surgery
Key actions of PTH?
- hypercalcaemic
- hypophophatemic
- renal tubular reabsorption
- bone reabsorption
- GI tract absorption (incr renal generation of active vit D which then acts on the gut)
- via reduced tubular reabsorption
Which form of vitamin D is measured
fdsfds
What is vitamin D called in the kidney?
Calcitriol (active form of bit D)
When is calcitriol used therapeutically?
In patients with renal failure (generally not used as a supplement because wuite expensive)
What is the active form of bit D?
1,35 - Vit D
What is main action of active vit D?
Incr gut (and kidney) calcium reabsorption
Why do we not measure the ionised form of calcium normally when that is the form that is physiologically active?
Hard to measure
How much of total serum calcium is ionised? Why can measuring total calcium cause problems? How do you overcome it?
45%
Disturbances in albumin (normally 10% of total calcium is bound to albumin) can > misinterpretation
Measure albumin
Threat to calcium homeostasis
- abnormal vit D metabolism?
Intake
Synthesis
Metabolism to 1,25 - dihydroxyvitamin D
What is the calculation for adjusted calcium?
Total calcium + 0.02 (40-albumin)
Mem aid for hypercalcaemia?
Bones (fractures), stones (kidney stones), abdominal groans and moans (psych)
Most common causes of hypercalcaemia
Malignancy
Primary hyperparathyroidism
Why is PTH important for hypercalcaemia interpretation? Meaning of each?
If PTH is suppressed, that is a normal response. Causes of hypercalcaemia
- Malignancy
- Vit D excess
- Sarcoidosis (cells produce vit D)
If PTH is raised (or inappropriate)
- primary or tertiary hyperparathyroidism (+ calcium receptor defects e.g. familial hypocalcuric hypercalcaemia)
