We hypothesized that Io-PTH levels would decline to normal or near normal after successful parathyroidectomy.

Evaluate efficacy and predictive factor of parathyroid hormone measurement during parathyroid resection.

Every Io-PTH level from 2001-10 at a single institution was evaluated. Charts were reviewed for preoperative diagnosis, final Io-PTH level, unilateral or bilateral exploration, calcium and parathyroid hormone levels.

225 patients underwent 594 Io-PTH measurements. 16 patients were excluded. Final Io-PTH levels were normal (< 65 pg/mL) in 189 patients and elevated in 20 patients. 12 of 20 patients with elevated final Io-PTH levels had > 80% decrease, so that 201 patients had Io-PTH levels that were normal or dropped by > 80%. 8 patients had Io-PTH levels that dropped by < 80%, 4 of whom had < 50% decline. Normal or near-normal Io-PTH level after resection of a parathyroid adenoma allowed unilateral exploration in 146 patients. Persistent elevation of Io-PTH levels led to bilateral exploration in 22 patients.

Io-PTH levels should become normal or to drop by at least 80% during successful parathyroidectomy. Persistent elevations of Io-PTH after resection of an abnormal gland dictate the need for bilateral exploration.