Parathyroidectomies using intraoperative parathormone monitoring: when should we stop measuring intraoperative parathormone levels?

Intraoperative parathyroid hormone monitoring (IOPM), in use for the last 15 years, has facilitated focused parathyroidectomy. We undertook this study to determine if a drop in IOPT hormone levels below 50 per cent of baseline were sufficient to terminate the procedure. We conducted a retrospective chart review (January 2007 to September 2010) of 104 patients who underwent initial parathyroidectomies with IOPM by general surgeons for primary hyperparathyroidism. Patients were followed up for serum calcium levels (range, 6 to 48 months). The number of specimens excised was significantly decreased when IOPT hormone levels dropped to greater than 50 per cent and came within the normal range earlier. Moreover, for single-gland parathyroid adenomas, once the parathyroid hormone values dropped to less than 50 per cent in the 5-minute sample, they continued to decrease in the subsequent samples. In 23 cases requiring further exploration, the parathyroid hormone values had already decreased to greater than 50 per cent in 14 cases but had not normalized (reference range, 8 to 74), leading to additional exploration. However, subsequent pathologic analysis showed that the initial gland removed was the adenoma in all these cases. A drop in the initial 5-minute parathyroid hormone value to less than 50 per cent of the baseline should serve as sufficient evidence to terminate the procedure. This would translate into significant laboratory and personnel cost savings over time. However, this should be carefully correlated with preoperative ultrasound/sestamibi findings.