Measures of PTH Predict Post-Thyroidectomy Hypocalcemia

Heidi Splete

October 01, 2023

Postoperative parathyroid hormone (PTH) showed 100% sensitivity in predicting post-thyroidectomy hypocalcemia, according to the results of a prospective study of 60 patients.

Post-thyroidectomy hypocalcemia remains a major complication in patients who have undergone total thyroidectomy, and early identification can reduce disease burden and improve outcomes, according to Ahmed Sobhy Youssef, MD, of the University of Oklahoma Health Sciences Center, Oklahoma City, and colleagues.

In a presentation at the annual meeting of the American Academy of Otolaryngology-Head and Neck Surgery, Youssef presented results of the study which looked at early post-operative parathyroid hormone as a predictor of post-thyroidectomy hypocalcemia.

Dr Ahmed Sobhy Youssef

During his fellowship in Oklahoma in the wake of the COVID-19 pandemic, Youssef observed a wide variation in follow-up for calcium levels after thyroidectomy. "Some surgeons will order PTH and ionized calcium 4 hours after surgery, others would order later, at 6-8 hours," he told Medscape Medical News. However, "all patients would be admitted for 1-2 nights [before being] discharged home, which meant more restrictions on the number of beds allowed for our head and neck cancer service."

Discussion with his department chair led to a literature review seeking strategies to discharge patients earlier, and Youssef developed the idea for early PTH testing.

The study population included 60 adults who underwent thyroidectomy for benign or malignant disease at a single center between January 2022 and January 2023. The researchers measured PTH at 1 hour after surgery and compared it to results of a standard postoperative measure at 4 hours after surgery.

The researchers found a significant positive correlation between PTH measured 1 hour after surgery and ionized calcium (Ca) at 4 hours. The sensitivity of the early PTH assay, defined as "measured below 14 pg/ml," was 100% to detect hypocalcemia, with an area under the curve (AUC) of 0.797.

"The results were amazing," said Youssef. "We found that when we measure PTH as early as 1 hour after total thyroidectomy, while patients are still in recovery, PTH was very sensitive to predict hypocalcemia." The correlation was strong with measures at 4 hours.

"Our takeaway message is the 1-hour level PTH is very reliable in predicting hypocalcemia," he added. This measure can serve as a guide for discharging patients the same day, with instructions to return if they develop any symptoms of hypocalcemia.

The use of early PTH also helped to reduce hospital admissions and identified patients who were eligible for same-day discharge with no need for additional replacement medications, Youssef said.

So far, "we have had no readmissions for thyroidectomy patients since we started to follow this protocol at our institution," he noted.

The findings were limited by the relatively small sample size, and more research is needed. However, the results suggest that early measurement of PTH at 1 hour after surgery is an accurate predictor of hypocalcemia in total thyroidectomy patients.

"I strongly recommend high thyroidectomy volume institutions apply the same protocol and publish their data about that, so we can come up with a consensus/guideline for management of calcium following thyroidectomy," Youssef said.

More Proof of PTH's Predictive Power

"The utility of postoperative PTH for predicting symptomatic hypocalcemia is beneficial for guiding postoperative management of patients following total thyroidectomy," said Larissa Sweeny, MD, of the University of Miami, Florida, who served as a moderator for the session in which the study was presented.

"Proper identification of patients that require supplemental medications following surgery reduces administration of medications to patients that do not require supplemental medications," Sweeny told Medscape Medical News.

In addition, better identification not only ensures that the patients who do require supplemental medications receive them, but also reduces postoperative complications and readmissions, she said.

For clinical practice, the current study "reinforces the utility of postoperative PTH lab values for guiding medication administration following total thyroidectomy," said Sweeny. "I have been using postoperative PTH lab values following total thyroidectomy to guide my postoperative management of these patients for over 6 years." 

However, looking ahead to additional research, "Correlation with dosage of supplemental calcium and duration to return of normal PTH would be helpful information," Sweeny said.

The study received no outside funding. The researchers and Sweeny report no relevant financial relationships. 

OTO-HNSF 2023. Early Postoperative PTH Determination as Predictor for Post-thyroidectomy Hypocalcemia. Presented October 1, 2023. Best of the Scientific Orals 1.

For more news, follow Medscape on Facebook, X (formerly Twitter), Instagram, YouTube, and LinkedIn


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.