Intraoperative Parathyroid Hormone (PTH) Monitoring
Intraoperative PTH monitoring
Parathyroidectomy guided by intraoperative PTH monitoring has several advantages over traditional bilateral neck exploration, namely, minimal neck dissection allowing same-day discharge with similar or higher success rates and shorter operative time with fewer risks and complications. Based on a vast number of reports showing that the operative success following parathyroidectomy guided by intraoperative PTH monitoring is similar or even higher than traditional bilateral neck exploration achieved with the benefits described above, this approach should be considered the procedure of choice for treatment of sporadic primary HPT.
Intraoperative parathyroid hormone (PTH) monitoring was first suggested by Nussbaum et al in 1988 when they described a decrease in PTH levels following excision of parathyroid adenomas in patients with sporadic primary hyperparathyroidism. In 1991, George L. Irvin III, MD, an endocrine surgeon and professor of surgery at University of Miami, published for the first time in the English-language literature a series of 21 patients who underwent parathyroidectomy with real-time PTH monitoring during the procedure, showing that this assay was accurate in predicting postoperative calcium levels. Since its introduction more than 15 years ago by Irvin, focused parathyroidectomy guided by Intraoperative Parathyroid Hormone (PTH) Monitoring became a standard procedure to treat patients with primary hyperparathyroidism . It explains by the fact that about 85% of patients with primary hyperparathyroidism will have single parathyroid gland disease, called an adenoma, that is responsible for elevated PTH level and hypercalcemia, and minimally invasive approach is justified.
Advantages of focused parathyroidectomy include improved cosmetic results with smaller incisions, decreased pain, shorter operative time, ambulatory surgery, decreased hospitalization, rapid postoperative recovery, decreased postoperative hypocalcemia.
“Rapid” PTH assays only measure PTH levels at specific time points during parathyroidectomy as determined by the surgeon. It is therefore paramount to understand hormone dynamics during parathyroidectomy to properly request blood sampling at specific intervals during neck exploration. Intraoperative PTH monitoring helps the surgeon by: (a) confirming complete excision of all hyperfunctioning parathyroid tissue before the operative procedure is finished, without visualization of normally functioning parathyroid glands; (b) pointing out the presence of additional hypersecreting tissue by an insufficient PTH drop, indicating that further exploration is needed to achieve operative success; (c) differentiating parathyroid from nonparathyroid tissues with biochemical confirmation of fine-needle aspirations; and (d) identifying the side of the neck containing the hypersecreting parathyroid gland(s) with the use of differential jugular venous sampling.
Surgical Implementation of PTH Monitoring
When the original “>50% PTH drop” criterion is used, a peripheral PTH level falling more than 50% from the highest value—either preincision or pre-excision value—10 minutes after removal of all abnormal parathyroid glands predicts postoperative normal or low calcium levels with excellent accuracy of 97% to 98% (14-18). While waiting for PTH results to be reported, which can range from 8 to 20 minutes (depending on the assay used and its physical location), the surgeon may proceed with closure of the cervical incision, avoiding manipulation of the remaining parathyroid glands in an effort to minimize the chance of falsely elevating PTH levels and a delay in hormone drop. Usually, during the closure of the incision, 0- and 5-minute PTH levels are reported, which is the reason PTH is measured at the 5-minute interval. If the 5-minute PTH level decreases sufficiently, the procedure can be finished without further neck exploration. When a point-of-care PTH assay is used, the 10-minute PTH level is reported by the time of extubation confirming operative success. Conversely, if the criterion is not met with the 10-minute sample, the neck is re-explored and the protocol for blood sampling is repeated for each additional excised gland until all hypersecreting tissue is removed as indicated by the adequate PTH drop. If no significant PTH drop occurs in 5 or 10 minutes, cervical incision should be reopened and re-exploration should be performed for additional hypersecreting tissue.
I do perform intraoperative parathyroid hormone (PTH) monitoring in all parathyroidectomy procedures. Blood tests for PTH measurements are taken right during the surgery. There are at least 4 time points for measurement: right before surgery (baseline level), during removal of the parathyroid adenoma (T-0 level), and in 5 and 10 minutes after removal of adenoma (T-5 and T-10 levels). Intra-operative parathyroid hormone monitoring determines the cure if either T5 or T10 levels dropped more than 50% compare to either T-baseline or T-0 levels after removal of the adenoma ("Miami criteria" developed by Dr. Irving). Intraoperative PTH Monitoring does not fail to recognize other hypersecreting glands that, if not removed, may lead to higher rates of operative failure or late disease recurrence.
On the picture bellow you can see technician who is assigned to my surgeries and performs intraoperative PTH measurements in operating room during each parathyroid procedure.
Parathyroid hormone (PTH) monitoring during parathyroid surgery (laboratory is set up next to my operating room)
Parathyroid hormone (PTH) monitoring during parathyroid surgery (tubes)
Lew JI, Irvin GL 3rd. Focused parathyroidectomy guided by intra-operative parathormone monitoring does not miss multiglandular disease in patients with sporadic primary hyperparathyroidism: a 10-year outcome. Surgery. 2009 Dec;146(6):1021-7.
Irvin GL, Carneiro DM, Solorzano CC. Progress in the operative management of sporadic primary hyperparathyroidism over 34 years. Ann Surg. 2004;239:704–708.
Grant CS, Thompson G, Farley D, et al. Primary hyperparathyroidism surgical management since the introduction of minimally invasive parathyroidectomy: Mayo Clinic experience. Arch Surg. 2005;140:472–478.
Denise Carneiro-Pla, "Contemporary and Practical Usef of Intraoperative PTH Monitoring". Endocr Pract. 2011;17[Suppl 1]:44-53