Week 5 - Calcium and Renal stones Flashcards
How much of the Ca in the kidney is reabsorbed? Where does this occur?
- 95-98%
- 65% paracellular in PCT
- 25% in ascending LoH
- 10% in DCT under PTH
What is the connection between kidney and vitamin D?
-The kidney hydroxylates 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol (active vit D) via 1a-hydroxylase
What are the functions of active Vit D3?
- Increase bone resorption
- Increase Ca uptake from gut
- Increase resorption in kidneys
What controls hydroxylation of active vitamin D?
-PTH which is under negative feedback by Ca and Pi
What are the functions of PTH?
- Increase 1a-hydroxylase
- Aids bone remodelling by stimulating osteoclastic activity and slowly osteoblastic activity (to release cytokines to stimulate osteoclasts)
- Increases Ca resorption in kidney
What is the function of calcitonin?
-Decrease Ca resorption
How do Ca and Pi feedback on PTH?
-High levels of Ca or PTH bind to receptors on PT cells and inhibit/stimulate its release
What is the main cause of hyperparathyroidism? How does it cause hypercalcaemia?
- Parathyroid adenoma
- Excess PTH secretion causes continual Ca resorption despite plasma concetration
What are the symptoms of hypercalcaemia?
- Stones -> real calculi
- Moans -> Depression and cognitive difficulty
- Groans-> constipation
Name a malignancy why commonly causes hypercalcaemia
-Squamous cell carcinoma of lung due to secretion of PTHrp
How do you treat hypercalcaemia?
-Hydration and loop diuretics
What are the symptoms of hypocalcaemia?
- Hyperexcitability of NMJ leading to tetany
- Paralysis, coma, death
Where can renal stoned lodge?
-Anywhere along UT but most common at pelviuretic junction, pelvic brim or ureteric orifice
Who are renal stones more common in?
-Men
What are the main types of renal stone?
- Calcium
- Magnesium ammonium phosphate
- Uric acid
