Hypercalcaemia and primary hyperparathyroidism

Patients with parathyroid carcinomas are more likely to have a marked hypercalcaemia with very high serum PTH levels.

A 24-hour urine collection should be sent for creatinine clearance and calcium measurement.

Imaging

Patients with confirmed primary hyperparathyroidism should also have a renal ultrasound at baseline to look for renal calculi.

Ultrasound of the neck and ^99m technetium sestamibi scan (Fig. 25.1) should be performed as part of preoperative localization when surgical intervention is indicated (see below).

More extensive preoperative imaging including magnetic resonance imaging, computed tomography, angiography and selective venous sampling may be required in patients with recurrent disease or ectopic parathyroid adenoma (e.g. mediastinal, intrathyroid, lateral neck, retro-oesophageal).

Treatment

The only curative treatment for primary hyperparathyroidism is surgery. However, surgery is not appropriate in all patients. The potential benefits must be weighed against the risks in each case.

Figure 25.1 A left inferior parathyroid adenoma on a sestamibi scan.

Indications for surgery

Guidelines for surgical intervention have been developed based on risk of disease progression and end-organ effects. Parathyroidectomy improves bone density and may have modest effects on some quality of life symptoms. The US National Institutes of Health guidelines (2002) for surgical intervention include:

symptomatic patients
asymptomatic patients with:

— A ge below 50 years (in a study of patients treated conservatively over 10 years, the disease progressed in 27% of asymptomatic patients, most of whom were younger than 50 years and age was the only predictive index)

— Bone mineral density: T-score less than –2.5 (hip, spine, forearm)

— Calculi (renal stones)

— Creatinine clearance reduced by 30%

— Difficult to do follow-up periodically

— Elevated serum calcium more than 0.25 mmol/L above the upper limit of normal or 24-hour urinary calcium above 10mmol. This is a relative indication for surgery. It is recognized that urinary calcium excretion correlates poorly with the development of renal stones.

It is important to note that the National Institutes of Health guidelines do not apply to familial primary hyperparathyroidism syndromes.

Bilateral neck exploration

Parathyroidectomy should be performed only by surgeons who are highly experienced and skilled in this operation. The standard surgical approach for most patients is bilateral neck exploration with identification of all four glands, usually under general anaesthesia. The amount of parathyroid tissue removed varies with the cause of hyperparathyroidism:

The gland containing a parathyroid adenoma is removed. The other glands may be biopsied.
For four-gland hyperplasia, three and one-half glands are removed, leaving one-half of the most normal-appearing gland marked with a clip.
In patients with MEN type 1, total parathyroidectomy may be performed (with surgical implantation of parathyroid tissue in the forearm in some centres) because of the high recurrence rate.

Minimally invasive parathyroidectomy

Minimally invasive parathyroidectomy may be the procedure of choice in patients with unilateral pathology (detected by imaging), with no family history of MEN and in the high-risk elderly.

Minimally invasive parathyroidectomy may be performed if ^99m technetium sestamibi and ultrasound scans both show an adenoma in the same location (‘concordant’ imaging). The location is marked on the skin, and surgery is performed through a 2–4 cm incision under local anaesthetic.

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