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INVESTIGATION OF SUSPECTED HYPERPARATHYROID DISEASE

Interpretative comments on reports:

If patient hypercalcaemic, the following comments will be added to non-endocrinologist reports.

PTH

Comment

>6.9

Raised PTH, suggestive of primary hyperparathyroidism. Suggest referral to endocrinologist.

2.6-6.9

Normal PTH, consistent with primary hyperparathyroidism. Familial benign hypercalcaemia should be considered. Suggest referral to endocrinologist

<2.6

Borderline low PTH, consistent with non-parathyroid cause of hypercalcaemia.

<1.6

Low PTH, consistent with non-parathyroid cause of hypercalcaemia

All patients (excluding secondary HPTH in renal dialysis) should be referred to Endocrinology team for further evaluation:

1.

Confirm raised corrected calcium and PTH on fasting sample

2.

Exclude FBH if PTH less than 7.5 pmol/L (Calcium excretion)

3.

Exclude phaeochromocytoma (24hr. urinary catecholamines)

PREVALENCE OF FAMILIAL BENIGN HYPERCALCAEMIA

1 in 200 cases of hypercalcaemia1, 1 in 20 cases of hypercalcaemia if PTH (mid molecule specificity) is raised (>6.9) and 1 in 4 when PTH is between 2.6 and 6.9 pmol/L2

CALCIUM EXCRETION

Urine excretion is low in FBH. Using fasting serum and 2nd void urine sample the calcium excretion (fasting urine calcium:creatinine ratio x serum creatinine) at a cut-off of 22 gives a sensitivity 95% and a specificity 92% for FBH.

(24hr urine calcium - cut-off 5.1 mmol/l; sensitivity 95% and specificity 63% for FBH)3.

REFERENCES

1.

Marx SJ. Familial hypocalcuric hypercalcaemia. In Heath and Marx, eds. Clinical Endocrinology, Vol 2, Calcium disorders. London: Butterworth Scientific, 1982: 217.

2.

Gunn IR. Familial benign hypercalcaemia - an under-diagnosed condition? Proc UK NEQAS Meeting 1998; 3: 85-89.

3.

Gunn IR, Wallace JR. Urine calcium and serum ionized calcium, total calcium and PTH concentrations in the diagnosis of primary hyperparathyroidism and familial benign hypercalcaemia. Ann Clin Biochem 1992; 29: 52-8.

 

Reviewed by: Tony Everitt, Consultant Biochemist
Last edited 07/08/08