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BOSTON -- Certain factors may help predict which patients may be at risk for permanent hypoparathyroidism (PHypoP) after thyroidectomy, researchers reported here.

In an analysis of 176 patients who underwent a total thyroidectomy, a total of 17% (n=30) of patients developed PHypoP, according to Steven Brown, DO, of the University of Texas Health Science Center at San Antonio, and colleagues.

Those who had both low parathyroid hormone (PTH) levels and low calcium (Ca) levels reported the highest rate of developing PHypoP compared with other groups of patients:

• Low PTH/low Ca: 30.3% of group developed PHypoP (P=0.0007)
• Normal PTH/low Ca: 19.4%
• Low PTH/normal Ca: 10.0%
• Normal PTH/normal Ca: 2.0%

Compared with the other groups, patients with low PTH and low calcium had a 4.3 higher odds of developing PHypoP (95% CI 1.9-9.9), Brown said in a presentation at the American Association of Clinical Endocrinologists (AACE) annual meeting.

The researchers also found those who developed PHypoP experienced a significant drop in PTH (69.7% vs 29.7%, P=0.016) and calcium levels (17.8 % vs 14.3%, P=0.042) following surgery, which was not seen in patients who did not develop the condition.

"Predicting patients at-risk for permanent hypoparathyroidism is key to managing postoperatively," Brown said, adding that "It's very important to draw both pre-operative labs and also post-operative labs in order to help predict those patients who are at risk for permanent hypoparathyroidism."

"Calculating percent of change, which we typically don't do after surgery, can also assist us in predicting those patients, in order to get the right patients on the right medications for the right duration of time after surgery," he added.

For the retrospective study, Brown's group reviewed 250 charts of patients from a single tertiary center who underwent a total thyroidectomy from 1999 to 2013 due to thyroid cancer. Preoperative lab values for serum calcium, PTH, vitamin D, and albumin levels were assessed, and postoperative values were assessed 1, 6 and 12 months after surgery.

The group defined PHypoP as persistently low PTH and calcium levels for >6 months after total thyroidectomy, with or without requiring calcitriol to maintain normal calcium levels.

All patients were further divided into one of four categories outline above, separated according to lab values immediately after the procedure. A low PTH was defined as an intact PTH <12 pg/mL, while low calcium levels were considered a serum calcium <8.0 mg/dL.

Preoperative lab values for PTH, calcium, and vitamin D were not found to be predictive of PHypoP after surgery, however. Also, there were no differences between patients who developed PHypoP and those who did not in regards to race, ethnicity, sex, or age.

David Lieb, MD, AACE abstracts committee co-chair, asked if these findings prompted any changes care deliverance. Lieb is from the Eastern Virginia Medical School in Norfolk.

Brown answered affirmatively, stating,"we're starting to incorporate some of these practices into our patient care, particularly for those with papillary thyroid cancer," adding that the next phase of research will be to conduct a prospective study at three different institutional sites.

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