Clinical Calcium Homeostatis Flashcards
what are the general functions calcium is needed for in the body
bone formation
cell division and growth
muscle contraction
neurotransmitter release
what percentage of calcium is found in the intracellular fluid
0.9%
what percentage of calcium is found in the extracellular fluid
0.1%
in plasma, what proportion of calcium is bound to albumin
45%
in plasma, what proportion of calcium is ionised
45%
what is the normal range of plasma calcium
220-2.60 mMol/L
what effect does increased albumin have on free calcium
increased albumin decreases free calcium
what effect does decreased albumin have on free calcium
decreased albumin increases free calcium
how do we calculate free plasma calcium if it is not 40g/l
Adjust Ca2+ by 0.1mmol/l for each 5g/l reduction in albumin from 40g/l
what effect does acidosis have on ionised calcium
acidosis increases ionised calcium thus predisposing to hypercalcaemia
what cells of the parathyroid gland secrete parathyroid hormone
cheif cells
what triggers chief cells to produce PTH
chief cells respond directly to changes in calcium concentration. PTH os secreted in response to a fall in calcium
what effects does PTH have on calcium at the renal tubules
promotes reabsorption of calcium from renal tubules
what effect does PTH have on bone
promotes reabsorption of calcium from bone
what effect does PTH have on vitamin D
converts vitamin D from its inactive form to active
what neuromuscular clinical features may you find in acute hypocalcaemia
paresthesia
muscle twitching
seizures
laryngospasm/bronchospasm
what cardiac clinical features may you find in acute hypocalcaemia
prolonged QT hypotension heart failure arrythmia papilloedema
what clinical features may you find in chronic hypocalcaemia
ectopic calcification
extrapyramidal signs
dementia
what can cause hypocalcaemia
disruption of parathyroid gland
severe vitamin D deficiency
Mg2+ deficiency
pancreatitis
what can cause low parathyroid hormone
genetic disorders
post surgery
autoimmune
what can cause high PTH
vitamin D deficiency
renal disease
pancreatitis
when investigating hypocalcaemia what important things should be asked in the history
neck surgery
autoimmune disorders
ca2+ and Vit D intake
what investigations should be done for hypocalcaemia
ECG serum calcium albumin phosphate PTH U&E's Vit D Magnesium
what can cause hypoparathyroidism
digeorge syndrome
destruction
infiltration
reduced secretion PTH
what is pseudohypoparathyroidism
disorder that presents in childhood, defined by target organ unresponsiveness to PTH
what are Ca2+ PO4- and PTH levels in pseudohypoparathyroidism
low Ca2+
high PO4-
elevated PTH
severe hypocalcaemia is a medical emergency what level would Ca2+ be
<1.9mmol/l
what is the treatment for severe hypocalcaemia
IV calcium gluconate
what Ca2+ level in hypercalcaemia requires urgent treatment due to risk of dysrhythmia and coma
> 3.5mmol/L (requires urgent correction due to risk of dysrhythmia)
what are causes of hypercalaemia
primary hyperparathyroidism
MEN syndromes
tertiary hyperparathyroidism
hypercalcaemia of malignancy
Vit D intoxication
what are clinical features of hypercalcaemia
polyuria
polydipsia
nephrolithiasis
anorexia
nausea&vomiting
constipation
muscle weakness
what are neurological features of hypercalcaemia
decreased concentration
fatigue
confusion
what are cardio features of hypercalcaemia
shortening of QT interval
bradycardia
hypertension
what should be looked out for during examination in hypercalcaemia
signs of underlying malignancy
what investigations should be done for hypercalcaemia
U&E's Ca2+ PO4- alk phosphate myeloma screen serum ACE PTH
what are the causes of 90% of hypercalcaemia cases
primary hyperparathyroidism or tertiary hyperparathyroidism
malignancy or drug causes
what investigations should be done for hyperparathyroidism
U&E’s check renal function
check for kidney stones
osteoporosis
Ca2+, PTH, vit D
what are the Indications for surgery in primary hyperparathyroidism
serum Ca2+ 0.25mmol/l above the normal limit
osteoporosis
eGFR<60 or presence of kidney stones
if <50 years
what is the treatment of primary hyperparathyroidism
generous fluid intake
cinacalcet (leads to a fall in PTH and therefore Ca2+ levels)
what is Familial Hypocalciuric
Hypercalcaemia
Autosomal dominant disorder of the calcium sensing receptor
benign disorder no therapy is needed
what is the treatment of hypercalcaemia
rehydration-consider dialysis if severe renal failure
after rehydration IV bisphosphonates
Bisphophonates are often prescribed for osteoprosis, what is their effect on Ca2+ levels
Bisphosphonates act to inhibit bone resorption therefore they can cause hypocalcemia
Multiple Endocrine Neoplasia (type 1 and 2) often presents with primary hyperparathyroidism true or false
true,
MEN type 1 (95%)
Men type 2 (20-30%)
