Improvements in parathyroid surgery in the intact 1-84 PTH assay era

Measurement of intact 1-84 parathormone (PTH) level by immunometric assays has been an important tool in the medical management of hypercalcaemia. The aim of the present study was to evaluate its practical contribution in the diagnosis and surgical treatment of primary hyperparathyroidism.

The results of surgery were compared (number of failed and inadequate cervicotomies, number of overlooked cervical glands) in two groups of primary hyperparathyroid patients operated on without (group I, n = 624) and with (group II, n = 360) intact PTH evaluation. The postoperative intact PTH level was measured 1-50 months after surgery in 109 unselected normocalcaemic patients. The benefit of intact PTH assay was studied in borderline patients. We tried to settle a correlation between parathyroid resected weight and intact PTH pre-operative level in different subsets of the disease.

The sensitivity for the diagnosis of primary hyperparathyroidism was 86.6% for intact PTH level alone, and 95.9% when plotted with synchronous serum total calcium. Hyperfunctional adenoma was incidentally discovered in 14 asymptomatic normocalcemic normo-PTH patients. The predictive positive value of intact PTH assay for the diagnosis of primary hyperparathyroidism was 99.3%. Intact PTH assay often affirmed the diagnosis of primary hyperparathyroidism in borderline cases. The postoperative intact PTH measurement was not a good indicator for evaluating the late outcome in seemingly cured patients. Sharp but statistically significant correlation was found between the resected weight and the intact PTH level. The discovery of a small adenoma in a patient with high intact PTH level, bone disease and low vitamin D level should raise suspicion of a second hyperfunctioning gland.

Intact PTH assay was a main contributor to the surgical management of primary hyperparathyroidism, reducing the number of unnecessary cervicotomies and enabling the cure of all cases of primary hyperparathyroidism except those due to mediastinal glands. It raised unanswered problems in the late postoperative course.