Primary Hyperparathyroidism is a common endocrine disorder. It is due to a single parathyroid adenoma in 80%, most of the remainder due to hyperplasia of all four parathyroid glands. The only curative procedure is a parathyroidectomy, but pre-operative localisation can be difficult. Isotope scanning with sestaMIBI is considered to be useful in localising any parathyroid adenoma to help guide surgery.
All patients having isotope parathyroid scans over a three year period at Barnet hospital were identified and the cases reviewed to determine the baseline biochemistry and ultimate treatment to asses the validity of such scanning.
18 scans were performed over 3 years. One was an inappropriate indication on review as the patient had secondary hyperparathyroidism secondary to osteomalacia. This patient was excluded from further analysis. Of the remaining 17 the average age was 65. Six patients were asymptomatic. The mean serum corrected calcium was 3.22 mmol per l plus/minus 0.91 (2.15-2.61). The mean PTH was 21.35 pmol per l plus/minus 26.56 (0.9-7.3)
Eight scans showed evidence of a dominant functioning parathyroid mass. Four patients had additional imaging modalities which confirmed a further 2 adenomas. Of these 10 patients, 6 proceeded to surgery and all were confirmed to have parathyroid tumours (5 adenomas and 1 carcinoma). One further patient is awaiting surgery.
There was a strong correlation between the PTH and serum calcium levels with a linear regression analysis (r=0.94 p<0.001).
MIBI scanning is a specific tool for diagnosing parathyroid adenomas in those with primary hyperparathyroidism in our hospital, although combination with Ultrasound detected more adenomas. We also demonstrated a strong correlation between the PTH level and the serum calcium level. However the isotope scan failed to detect an adenoma in about a half of patients with biochemical evidence of primary hyperparathyroidism.