Endocrine Abstracts

Primary hyperparathyroidism is one of the most common endocrine conditions affecting upto 2% of postmenopausal women. Diagnosis is primarily biochemical and is usually secure when a persistently elevated plasma calcium is found together with parathyroid hormone (PTH) concentrations above the middle of the normal range. The only other circumstance which can produce a similar picture is familial benign (hypocalciuric) hypercalcaemia (FBH) which is an inherited disorder oc calcium sensing. The distinction between these two conditions is generally made on the ratio of the clearance of calcium to that of creatinine in the urine after an overnight fast. Ratios below 0.01 indicate FBH whereas a ratio above 0.02 is usually associated with primary hyperparathyroidism. However in clinical practice it is often found that patients in which there is diagnostic confusion produce values between these two limits. The distinction is is potentially important as parathyroidectomy is contraindicated in FBH. However most cases of primary hyperparathyroidism in which there remains any doubt about the diagnosis are unlikely to satisfy the criteria for surgery.

Imaging of the parathyroids is not helpful in primary diagnosis. Indeed an experienced neck surgeon performing a full neck exploration will have a greater sensitivity for indentifying abnormal parathyroid glands than any of the currently available imaging techniques. Historically the use of such imaging has largely been confined to the investigation of patients following failed neck exploration. However, the more modern minimally invasive surgical techniques require indentification of the abnormal gland before surgery. Imaging techniques have therefore had a recent recrudescence with sestamibi scanning being the treatment of choice.