disorders of calcium metabolism Flashcards
in what form does most calcium exist in our body ?
mineral deposits in the skeleton and teeth
what are the different forms in which calcium circulates in the body ?
ionized : biologically active
bound to protein: mainly albumin , inactive
complexed to citrate and phosphate: biologically active
what is the role of calcium ?
skeletal strength neuromuscular condition stimulus secretion coupling second messenger within cells blood coagulation
of the circulating calcium in what form does calcium mostly exist in ?
ionized calcium
what is the role of calcitonin in calcium metabolism ?
calcitonin released from the parafollicular cells decrease the osteoclast activity
what is the effect of the parathyroid hormone ?
it allows for hypercalcaemia to occur through :
renal tubular reabsorption
increased in gut reabsorption
increased bone resorption
what is the effect of parathyroid hormone on phosphates?
reduces phosphate levels through reduced tubular reabsorption
what is the effect of vitamin D on calcium homeostasis ?
causes hypercalcaemia and hyperphosphataemia
how does vitamin D increase the levels of calcium and phosphate ?
through :
increased bone resorption
increased gut reabsorption
increased renal tubular reabsorption
what effect does calcitonin have on calcium homeostasis ?
decreases calcium levels
what are the clinical features of hypocalcemia ?
numbness, paraesthesia, muscle cramps, convulsions
cataracts
myopathy and bone pain
behavioural disturbances
positive trousseau’s sign and chovestek’s
what changes on the ECG would indicate hypocalcaemia ?
prolonged QT
what are the causes of hypocalcaemia ?
vitamin d deficiency renal failure hypoparathyroidism pseudohypoparathyroidism magnnesium depeltion acute pancreatitis massive blood transfusion artefactual
how does a patient with hypoparathyroidism present ?
hypocalcaemia and low or undetectable PTH
what would a non parathyroid cause of hypocalcaemia ?
hypocalcaemia and elevated PTH
what does renal failure lead to in relation to calcium homeostasis ?
low levels of vitamin D
high serum phosphate
reduced GI absorption
which eventually leads to elevated PTH
what does low vitamin D in the blood cause ?
osteomalacia
what is the diagnosis in a patient that has high PTH due to renal disease ?
secondary hyperparathyroidism
what do the lab investigations of a patient with tertiary hyperparathyroidism patient look like ?
elevated calcium levels
elevated parathyroid hormone levels
what are the clinical features of hypercalcaemia ?
usually asymptomatic polyuria , dehydration n anorexia, nausea, vomiting renal calculi peptic ulceration acute pancreatitis weakness
what are the commonn causes of hypercalcaemia ?
primary hyperparathyroidism
malignant disease
bony metastasis
what type of drug could cause hypercalcaemia ?
thiazide diuretics
what would the labs of a non parathyroid cause of hypercalcaemia look like?
hypercalcaemia
suppressed PTH
what would the labs of a PTH mediated cause of hypercalcaemia look like ?
hypercalcaemia
raise or detectable PTH
what are the three types of hyperparathyroidism ?
primary
secondary
tertiary
what does 1ry hyperparathyroidism look like ?
increased PTH , Increased calcium
what does secondary hyperparathyroidism look like ?
increased PTH , decreased calcium
what does tertiary hyperparathyroidism ?
increased PTH, increased calcium
what are the causes of 1ry hyperparathyroidism ?
PT hyperplasia
adenoma
cancer
part of MEN type 1
causes of 2ry hyperparathyroidism ?
diet
malabsorption
vit d deficiency
what are the causes of tertiary hyperparathyroidism ?
ESRF with chronic secondary PTH
post transplant
what is the treatment for 1ry hyperparathyroidism ?
surgery
what is osteomalacia and rickets a result of ?
a defect in bone mineralization secondary to vit D deficiency
what is the treatment for vit d deficiency ?
give cholecalciferol 20,000 IU once weekly for 6 weeks
then
800-1000 IU daily
what are the lab findings in osteomalacia and rickets ?
low serum calcium and phosphate
low vitamin D
high alklaline phosphate
high serum PTH ( secondary hyperparathyroidism)
