deck_1648553 Flashcards
Give five functions of Calcium
• Muscle contraction • Inactivation/activation of enzymes • Nerve conduction • Exocytosis • Hormone secretion • Haemostasis
What is the physiologically active from of Ca2+?
• Ionised form
Give the three forms in which Ca2+ is found in the body
• Free ionised species • Protein bound • Complexed
How much of dietary calcium is absorbed?
• 20-40% is absorbed (25mmol)
When does calcium absorption increase? (3)
• Growing children • Pregnancy • Lactation
How much calcium do the kidney filter per day?
• 250mmol
How much of the body’s calcium reservoir is found in the ECF?
• 1%
What chemical is responsible for the absorption of calcium from the gut?
• 1,25 - OH 2D control
Where is the majority of calcium reabsorption in the kidney?
• 65% reabsorbed in proximal tubule • 20-25% recovered in ascending loop of henle • 10% recovered in DCT under control of PTH
What is the standard 24hr urinary calcium excretion?
•
How much calcium filtered by kidney per day?
250 mmol
Give the actions of PTH
• Increases reabsorption in kidney • Increases breakdown of boneConverts calciferol to calcitriol in kidney
What is the inactive form of Calcitriol called?
Calciferol
What are the actions of calcitriol?
• Increase breakdown of bone • Increase reabsorption in kidneyIncrease absorption of calcium from gut
How is vitamin d2 produced?
• By gut
How is vitamin d3 produced?
• By skin
How does vitamin D become calciferol?
• Hydroxylation in the liver
When does calciferol become calcitriol?
• After 2nd hydroxylation
How is Calcium release regulated?
• Negative feed back to parathyroid gland • Gq receptor inhibit PTH release • Reduce further calcium absorption
What are the three major causes of hypercalcaemia?
• Primary hyperparathyroidism • Haemtological malignancies • Non-haematological malignancies
How do malignancies cause hypercalcaemia?
• PTHrp released • Does not convert calciferol to calcitriol
Give four systems that hypercalcaemia causes symptoms in
• Gastrointestinal • Cardiovascular • Renal • CNS
Give four gastrointestinal symptoms of hypercalcaemia
• Anorexia • Nausea/Vomiting • Constipation
Give three cardiovascular consequences of hypercalcaemia
• HypertensionShortened QT • Enhanced sensitivity to digoxin
Give three renal consequences of hypercalcaemia
• Polyuria • Polydipsia • Nephrocalcinosis
Give three cognitive effects of hypercalcaemia on the CNS
• Cognitive difficulties • Apathy • depression
Outline treatments for hypercalcaemia
General measures • Hydration - Increase Ca2+ excretion • Loop diuretics - Increase Ca2+ excretion Specific measures • Bisphosphonates - Inhibit breakdown of bone • Calcitonin - Opposes the action of PTHTreat underlying condition
What percentage of people will develop kidney stones in their life?
• 20% mean • 5-10% of women
What is the most common form of kidney stone?
• 70-80% made of calcium
What factors are involved in the formation of kidney stones?
• Low urine volume • Hypercalcuria Low urin pH
What does the mechanism of stone formation involve?
• Super-saturation of urine with calcium oxalate
What does conservative management of kidney stones involve?
• Increasing fluid intake • Restricting dieatary oxalate and sodium • Restrict calcium and animal protein
What calcium conc do we want to measure in the blood?
• Ionised calcium
What are the problems with measuring ionised calcium?
Degrades quickly
What hormone is responsible for calcium absorption from the gut?
Calcitriol (a derivative of vitamin D)
How is excess vitamin D stored?
• Converted to 24,25 - (OH)2 vitamin DInert
Why do people with HIV get vitamin D deficiency?
• Anti-retroviral treatment induces liver enzymes to break down vitamin D
Where is calcium reabsorbed in the most part?
• PCT - 65% • TAL - 25%
What three things regulate calcium reabsorption in the kidney?
• PTH • Vitamin D • Plasma Ca2+ levels
What can be used to treat hypercalcaemia that acts on the kidney?
• Loop diuretics which inhibit Ca2+ reabsorption
Whyshould thiazide not be used in hypercalcaemia?
• Increases Ca2+ reabsorptio in kidney
What percent of men get renal stones?
• 20%
What is the main type of renal stone?
• Calcium
Give three types of renal stone other than calcium
• Magnesium Ammonium Phosphate • Urate • Cystine
What is gout?
• Too much alcohol • Alcohol competes with urate in kidney • Urate accumulated in tissues
Give five promoters of kidney stone formation?
• Urine supersaturation with calcium oxalate • Low ionic strength • Low citrate • Magnesium • Low pH
What is nephrolithiasis?
• Calculi in the kidney
What is the classic presentation of kidney stones?
• Loin to groin pain • Renal colic • Hydronephrosis
