Intra-operative parathyroid hormone kinetics and influencing factors with high baseline PTH: a prospective study


Correspondence: Dr Amit Agarwal, Professor, Department of Endocrine Surgery, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Raebareli Road, Lucknow 226014, India. Tel.: +919335291120;Fax: +91 (0522) 2668078, 2668017; E-mail:


Background and objective

Intra-operative parathyroid hormone (IOPTH) kinetics and therefore the efficacy of IOPTH utilization as a predictor of cure are likely to be affected by baseline IOPTH levels, vitamin D deficiency and parathyroid weight.

Patients and methods

Consecutive subjects with primary hyperparathyroidism (PHPT, n = 51) undergoing parathyroidectomy with IOPTH monitoring were studied prospectively during the period October 2009–November 2011. Samples were collected pre-incision, pre-excision and post-excision (5, 10, 15 min). Iterative analysis of IOPTH kinetics and half-life calculation was carried out in subgroups. Nonparametric testing was used for group statistics.


Hypovitaminosis D (25(OH)D3 < 50 nm) was present in 39 (76%), serum PTH > 1000 ng/l in 23 (45%), and giant parathyroid adenoma (weight > 3000 mg) in 23 (45%). The percentage drop at 10 min was significantly higher in large adenomas (weight > 3000 mg). Miami and 5 min criteria showed the highest negative predictive value and maximum accuracy. The average percentage IOPTH drop observed at 5 min post-excision was 79·8%. Kinetic analysis showed a mean half-life of PTH of 2·57 ± 0·27 min (range: 0·07–11·55).


IOPTH monitoring is reliable even in patients with extremely high baseline IOPTH value, with a greater percentage drop at 5 and 10 min post-excision. In patients with high baseline IOPTH, a 50% decay in PTH value at 5 min may be indicative of cure, obviating the need for 10 and 15 min samples. IOPTH kinetics are altered by adenoma weight but not affected by vitamin D status or baseline IOPTH levels.