hyperparathyroidism Flashcards
definition of hyperparathyroidism
primary - increased secretion of PTH regardless of Ca
secondary - increased PTH secondary to hypocalcaemia
tertiary - autonomous PTH secretion following chronic secondary hyperparathyroidism
aetiology of primary hyperparathyroidism
parathyroid gland ademoma, or hyperplasia (80% single adenoma, 18% hyperplasia/multiple adenoma)
parathyroid carcinoma (2%)
may be associated with multiple endocrine neoplasia (MEN 1)
aetiology of secondary hyperparathyroidism
chronic renal failure
vit D deficiency
what is MEN type 1
mutation in menin gene on chr 11
- parathyroid adenoma or hyperplasia
- pancreatic endocrine tumours
- pit adenomas
what is MEN 2
mutation in RET gene on chr 10
- medullary thryoid carcinoma
- phaeochromocytoma
- parathyroid hyperplasia (MEN-2A)
- mucosal neuromas on lips and tongue (MEN-2B)
epidemiology of hyperparathyroidism
primary
5 in 100000/yr
females more
40-60yrs
presenting sx of primary hyperparathyroidism
asymptomatic when mild hypercalcaemia
polyuria bnut dehydrated
polydipsia
renal calculi
bone pain, fractures, osteopenia/porosis
abdo pain
pancreatitis
ulcers - duodenal more than gastric
nausea
constipation
psychological depression
lethargy
weak
HTN
presenting sx of secondary hyperparathyroidism
symptoms of hypocalcaemia
underlying cause - chronic renal failure/vit D deficiency
Ix for hyperparathyroidism
UE
serum Ca - high in primary/tertiary, low/normal secondary
phosphate - low in primary (unless in renal failure)/tertiary, high secondary
albumin - to calculate corrected ca
high ALKPHOS (from bone activity)
vit d - low in secondary
PTH levels - high/normal in primary, high in secondary
when parathyroid carcinoma - more likely to have marked hypercalcaemia with high serum PTH levels
primary - hyperchloraemic acidosis (normal anion gap) - from PTH inhibition of renal tubular reabsorption of bicarb
urine analysis
renal US - renal calculi
radiograph (not routine)
preop localisation - US od neck and technetium sestamibi scan
DEXA
urine analysis in hyperparathyroidism
24hr high urine Ca
ddx includes familial hypocalciuric hypercalcaemia.
So if high/inappropriately normal PTH - Ca:creatinine clearance ratio measured to differentiate.
primary hyperparathyroidism (ratio>0.01) and FHH (ratio<0.01)
Calcium: creatinine clearance ratio:
- Urine calcium (mmol/L) [Plasma creatinine (mmol/L)/1000]
- Plasma calcium (mmol) Urine creatinine (mmol/L)
24hr urine collection should be sent for creatinine clearance and ca measurement
XR for hyperparathyroidism
osteitis fibrosa cystica because of severe resorption - rare
- subperiosteal erosion of phalanges
- cysts
- brown tumours (osteolucent bone defects)
- diffuse porotic mottling of skull - from demineralisation (pepper pot skull)
- acro-osteolysis
sclerosis of superior and inferior vertebral margins with central demineralisation (rugger jersey sign)
renal calculi/nephrocalcinosis
PTH in pts with hypercalcaemia secondary to malignancy, myeloma or granulomatous conditions (TB, sarcoidosis, lymphoma causing excess production of 1,25-dihydroxyvitamin D)
suppressed PTH
hypercalcaemia secondary to malignancy - treated with rehydration and IV pamidronate (a bisphosphonate).
FHH
Autosomal dominant disorder caused by inactivating mutations in the gene encoding the calcium-sensing receptor on the parathyroid cells and in the kidneys.
Mx for acute primary hyperparathyroidism
IV fluids (4-6 in 1st 24hr)
conservative Mx for primary hyperparathyroidism
when dont meet surgical criteria
avoid exacerbating factors - thiazide diuretics
adequate hydration (6-8 glasses of water a day) - to prevent stones
moderate Ca and vit D intake
surgical Mx of primary hyperparathyroidism
subtotal parathyroidectomy - prevents fractures and peptic ulcers
total parathyroidectomy in MEN1
indications: symptomatic or asymptomatic with ABCCrDE
- Age <50yrs
- BMD - T score <2.5
- calculi (renal stones)
- Creatinine clear reduced by 30%
- difficult to follow up
- elevated serum ca >0.25 mmol/L above upper limit of normal or 24hr urinary ca >10mmol
recurrence 8% over 10yrs
Mx of secondary hyperparathyroidism
secondary - treat underlying renal failure.
Ca and Vit D supplements
phosphate binders
cinacalcet if PTH >85pmol/L and parathyroidectomy tricky
complications of primary hyperparathyroidism
high PTH = high bone resorption, renal tubular Ca reabsorption, 1a-hydroxylation of vit D and intestinal Ca absorption = hypercalcaemia
complications of secondary hyperparathyroidism
increased sitimulation of osteoclasts and bone turnover = osteitis fibrosa cystica
complications of surgery for hyperparathyroidism
hypoparathyroidism
hypocalcaemia - hungry bones syndrome - check Ca daily for 14 days
recurrent laryngeal nerve palsy (<1%) = hoarse
prognosis for hyperparathyroidism
primary - surgery curative for benign disease in most cases
secondary or tertiary - as for chronic renal failure
sx and signs for hypercalcaemia
‘Bones, stones, groans, and psychic moans.’
Abdominal pain;
vomiting;
constipation;
polyuria;
polydipsia;
depression;
anorexia;
weight loss;
tiredness;
weakness;
hypertension,
confusion;
pyrexia;
renal stones;
renal failure;
ectopic calcification (eg cornea);
cardiac arrest.
ECG: reduced QT interval.
role/action of PTH
increases osteoclast activity - releasing Ca and phos from bones
increases Ca and decreases phos reabsorption from the kidney
•active 1,25 dihydroxy-vitamin D3 production is increased.
Overall effect is high Ca2+ and reduced phos
ddx for high ca and PTH
thiazides
lithium
familial hypocalciuric hypercalcaemia
tertiary hyperparathyroidism
primary hyperparathyroidism
