Calcium abnormalities - Hypercalcaemia Flashcards
list the causes of hypercalcaemia
PTH-mediated:
1. primary hyperparathyroidism (most-common cause)
Non-PTH-mediated:
- malignancy (2nd most common)
- granulomatous conditions, e.g. sarcoidosis, tuberculosis
- endocrine conditions, e.g. thyrotoxicosis, phaeochromocytoma, primary adrenal insufficiency
- drugs, e.g. thiazides, vitD and vitA
- inherited, e.g. familial hypocalciuric hypercalcaemia
- other, e.g. prolonged immobilisation, calcium-alkali syndrome, AIDS
describe the 4 possible mechanisms for hypercalcaemia of malignancy
- ectopic PTHrP production
- osteolytic metastases
- ectopic calcitriol (1,25-dihydroxyvitamin D) production
- ectopic PTH production
suggest possible symptoms caused by hypercalcaemia
<2.8 mmol/L
- polyuria and polydipsia
- dyspepsia (due to calcium-regulated release of gastrin)
- depression
- mild cognitive impairment
<3.5 mmol/L
- muscle weakness
- constipation
- anorexia and nausea
- fatigue
> 3.5 mmol/L
- abdo. pain
- vomiting
- dehydration
- lethargy
- cardiac arrhythmias - shortened QT interval
- pancreatitis
- coma
what can be the consequence of long-standing hypercalcaemia?
- calcium deposition into soft tissues
2. stone formation, e.g. nephrocalcinosis, nephrolithiasis or chondrocalcinosis
which investigations would you perform on a pt presenting with hypercalcaemia?
Bloods:
- corrected calcium level: increased (by definition) - compared with hypercalcaemia of malignancy, hyperparathyroidism is associated with lower serum calcium levels (<3 mmol/L) and a longer duration of hypercalcaemia (>6 mths)
- PTH, phosphate and ALP
- calcitonin: increased levels suggests B cell lymphoma
Bedside tests:
- urinary calcium and phosphate
Imaging:
- x-ray: may show features of bone abnormalities, e.g. demineralisation, bone cysts, pathological fractures or bony metastases
- KUB USS, CT or IV pyelogram: may be required to detect abnormalities of urogenital tract, e.g. stones, calcification
- parathyroid gland USS or technetium scan: may be indicated if hypertrophy or adenoma is suspected
Test results for a pt with hypercalcaemia show:
- serum phosphate: decreased
- serum ALP: normal/increased
- urine Ca2+: increased
- urine phosphate: increased
- PTH: increased
What is the diagnosis?
hyperparathyroidism
Test results for a pt with hypercalcaemia show:
- serum phosphate: decreased
- serum ALP: increased
- urine Ca2+: variable
- urine phosphate: increased
- PTH: variable
What is the diagnosis?
malignancy
Test results for a pt with hypercalcaemia show:
- serum phosphate: normal/increased
- serum ALP: normal/increased
- urine Ca2+: increased
- urine phosphate: normal
- PTH: decreased
What is the diagnosis?
granulomatous disease
Describe the immediate management for a pt with hypercalcaemia.
Tx should be initiated in hospital on advice of a specialist:
1. increase circulating volume with 0.9% saline, helping to increase UP of calcium.
After rehydration:
- bisphosphonates, e.g. pamidronate and zolendronic acid, to decrease bone turnover.
- glucocorticoids useful for hypercalcaemia due to vitD toxicity, sarcoidosis and lymphoma (decreased calcitriol production by activated mononuclear cells in granulomatous disease)
what is primary hyperparathyroidism?
Excess PTH production by 1 or more of the parathyroid glands, due to:
- single parathyroid gland adenoma (85%)
- 4 gland hyperplasia (10-15%)
- double adenomas (3-5%)
- parathyroid carcinoma (<1%)
Aetiology of adenomas or hyperplasia is largely unknown. Familial cases can occur as part of multiple endocrine neoplasia syndromes (MEN1 or MEN2a).
Describe the common symptoms of primary hyperparathyroidism.
Stones, bones, groans, moans, thrones and psychiatric overtones.
- kidney stones - most formed of calcium oxalate or calcium phosphate
- bone pain - due to increased PTH-mediated bone resorption
- lethargy and fatigue
- constipation and abdo. pain - decreased smooth muscle contraction (?excess cell membrane stabilisation)
- polyuria and polydipsia - ?downregulation of AQP
- confusion, depression, anxiety, etc.
