Calcium disorders Flashcards
What triggers secretion of PTH?
Low serum calcium levels or high phosphate
Actions of PTH?
Increased Ca absorbed in the distal tubule
Activates Vit D to give more calcium absorbtion
increased osteoclast activity to release ca from bone
Overall effect of increased PTH?
Increased Serum Ca and decr. phosphate
how is PTH regulated?
Transcription is inhibited by activated vit D
Translation is inhibited by serum CA
Where do we get Vit D from?
Diet: oilky fish, eggs
UV radiation: 7 dihydrocholesterol -> Vit D
Where is vit D hydroxylated?
first one is in the liver, second requires PTH in the kidney
What does the vit d assay look for?
25 oh D3, active frm is rarely measured
what does calcitonin do?
produced by thyroid C cells and released in hypercalcaemia. Inhibits resorption of bone by acting on osteoclasts, NOT essential to life
3 types of cell in bone?
osteoblast, marker is carbonic anhydrase
osteoclast, marker is alk phos
osteocyte
Normal calcium range
2.25-2.5
Presentation of hypercalcaemia?
Polyuria and polydipsia dyspepsia ( releases gastrin) depression mild cognitive impairment - Muscle weakness, constipation, anorexia - abdo pain, vomiting, dehydration, lethargy, shortened QT, coma, pancreatitis
renal stones and ulcers
Causes of Hypercalcaemia?
Common: HYperPTH
Malignancy- myeloma, mets, humoral hypercalaemia
Less common- vit D intoxication, familial hypocalciuric hypercalaemia, sarcoid,
Uncommon- thiazides, lithium, renal failure, vit A, milk alkali
Ix in Hypercalcaemia?
corrected calcium (tends to be longstanding and lower if non malignant) PTH
FOr underlying illness: cxr, bloods, Vit D, protein incl. serum electrophoresis, cortisol
end organ damage: renal US, skeletal radiographs. bone tumour markers
DIfferent types of hyperPTH?
1o: excessive secretion by gland, 80% are a single adenoma with 0.5% ca, association with MEN
2o: PT glands increase in activity due to low ca2+. chronic renal failure is the most common cause but also drugs such as lithium, thiazides- hypo as cannot activate vit D (kidneys fucked)
3o: usually when renal disease is corrected, hyperplasia then get hypercalcaemia when fixed. more likely to have hyper
Signs of hyper PTH?
relate to ca or asymptomatic weak, tired, depressed, thirsty renal stones, abdo pain, duodenal ulcers bone pain, #, osteoporosis check in hypertention
What can you see on imaging of hyperPTH?
osteitis fibrosa cystica (rare(, subperiosteal erosions, cysts, pepper pot skull in 3o
ix in hyperPTH?
diagnostic is high PTH in high/normal Ca
24hr urine collection will show raised ca, unless familial hypocalciuric hypercalcaemia
U+Es
Abdo kub for renal stones
dexa for osteoprosis
aim of ix in hyperPTH?
identify end organ damage and see candidates for surgery
Diagnosis of 1o PTH?
Ca>2.65 U+Es normal Not on lithium or thiazide PTH>3 24hy urinary CA >2.5
Management of hyperPTH?
observation in mild disease, see 6 monthly, increase fluid intake and avoid thiazides.
Medical: cinacalet (calcimomimetic) increases senstivity of cells to CA so PTH goes down (s/e myalgia and low test)
Surgery: prevents ulcers and fractures.
Indications for surgery in hyperPTH?
high serum ca high urinary bone disease renal calculi decr. renal fx <50
Complications of parathyroidectomy
metabolic: hypoparathyroid
hypocalcaemia
mechanical: tracheal compression from haematoma
r. laryngeal n damage
recurrance is 8% in 10 yr
Malignant hyperPTH?
PTrP is secreted by some squamous cell lung cancers and breast and renal. mimcs pth so incr, ca. PTH appears low as not detected on assay
Familial hypocalciuric hypocalcemia?
AD condition, reduced sensation to ca so think ca is normal when is actually high
generally benign and asymptomatic
dont benefit from surgery
Factors suggesting hypercalcaemia of malignancy?
low pth low albumin high alk phos raised PTrP increased PTH
Management of acute hypercalcaemia~?
Correct dehydration with saline
bisphosphonates- pamindronate slowly infused. 2-3 days to work, max effect 1 week
steroids are used in sarcoid eg pred 40-60mg
cemo may help in malignancy
