A large retrospective database study shows a high risk of hypocalcemia in bariatric patients who undergo subsequent thyroidectomy

Hypocalcemia is a major postoperative complication of thyroidectomy that can result in longer hospitalizations, increased cost of care, and negative impacts on patient outcomes and quality of life. A myriad of symptoms may accompany the clinical presentation of hypocalcemia, including numbness and tingling of the hands and lips, muscle cramps, tetany, laryngospasm, seizures, mood changes, altered mental status, cardiomyopathies, and prolonged QT intervals.¹ In addition, several studies indicate the risk of hypocalcemia following thyroidectomy is increased for patients with certain types of bariatric surgery, including a large retrospective study conducted at Penn State Health.

Dr. David Goldenberg, professor and chair of the Department of Otolaryngology-Head and Neck Surgery at Penn State Health Milton S. Hershey Medical Center and Penn State College of Medicine, and Dr. Jeff Lorenz co-authored a large retrospective study that hypothesized bariatric surgery patients were at increased risk of hypocalcemia following total thyroidectomy.²

“We published a study in 2017³ where we did a meta-analysis of available studies on the subject. We found that the entity of bariatric surgery as a complicator of subsequent thyroid surgery was limited to case reports and small series. Therefore, we embarked on the current study to study the subject on a large scale. It is important to shine a light on this so that bariatric surgeons, thyroid surgeons, and patients are aware of the risk and the ways to mitigate it,” Goldenberg said.

Understanding this was a problem, Goldenberg and Lorenz began an extensive retrospective database analysis of hypocalcemia risk in a sizable cohort of 49,395 patients to help bring awareness to the issue.

The researchers compared total thyroidectomy patients and hemithyroidectomy patients who had not had prior bariatric surgery to those with a history of surgery and subsequent thyroidectomy. The study adjusted for confounding factors: matching demographics and adjusting for the prior need for supplementation and other risk factors for hypocalcemia. The team also stratified bariatric procedures among Roux-en-Y patients versus sleeve gastrectomy surgeries. “We used a very large database spanning almost a decade,” Goldenberg said.

Roux-en-Y gastric bypass poses more risk

The study found a statistically significant increased risk of permanent hypocalcemia in patients who had Roux-en-Y gastric bypass, but not with sleeve gastrectomy surgery, compared to those with thyroid surgery who had no history of bariatric surgery.²

Goldenberg said he and his colleagues are trying to understand the mechanism behind the recalcitrant hypocalcemia better and why this occurs more often in patients with prior Roux-en-Y anastomosis than sleeve gastrectomy.

“We think it has something to do with the overall homeostasis of calcium and vitamin D in patients who undergo bariatric surgery,” Goldenberg said. “We hope to get the word out, so at least patients and the people performing the surgeries are aware of the increased risk.”

While there was a more significant number of patients with prior Roux-en-Y surgery and subsequent thyroidectomy who experienced short-term hypocalcemia, the risk was not statistically significant compared to those who had not had bariatric surgery. The reasons for the increased risk of recalcitrant but not short-term hypocalcemia in Roux-en-Y patients are unclear.

This study’s retrospective nature is a limitation; however, an advantage is that it is a large cohort and confirms the proposed hypothesis.

Positive implications

The obesity epidemic in America has translated to an increasing number of patients undergoing bariatric surgery. They were bringing awareness to the link between weight loss surgery and recalcitrant hypocalcemia after subsequent thyroid surgery is more relevant today than ever before. Through his research on hypocalcemia in this population, Goldenberg hopes bariatric surgeons, otolaryngology surgeons and endocrine surgeons will use the science to make informed decisions.

While Roux-en-Y anastomosis is still prevalent, some surgeons and patients are opting for less invasive or reversible types of bariatric surgery, such as gastric sleeve surgery or the Obera balloon procedure, which — according Goldenberg — may prove beneficial in patients who later require thyroidectomy when compared with Roux-en-Y anastomosis.

For surgeons performing thyroidectomies, asking patients if they have had prior bariatric surgery is an essential addition to the standard questions asked while obtaining a patient history. In addition, awareness of increased hypocalcemia risk in bariatric surgery patients may aid surgeons in appropriate patient counseling, preoperative care, and surgical planning, which Goldenberg has been doing for years. “If it is someone who had the old-style Roux-en-Y performed, then we have a much more in-depth conversation about this potential complication and to assure that they are calcium and vitamin D supplemented and before surgery,” he said.

Dr. Goldenberg ensures metabolic deficiencies are corrected as best as possible before thyroid surgery. He also notes that performing a thyroidectomy in two stages — doing a hemithyroidectomy and waiting a couple of months before completing the thyroidectomy — tends to result in less risk for recalcitrant hypocalcemia. The reason is still unclear, but it ensures that only two or four parathyroids are at risk at each surgery. “In many cases, if someone needs a total thyroidectomy, even for a papillary thyroid cancer which is incredibly slow growing, it is not unreasonable to do the necessary thyroid surgery in two stages,” Goldenberg said.

In an effort to prevent long-term hypocalcemia in patients with prior Roux-en-Y gastric bypass surgery, this study opens the door to some unanswered questions and potential changes to future surgical recommendations.

References:

1. Schafer AL, Shoback DM. Hypocalcemia: Diagnosis and Treatment. [Updated 2016 Jan 3]. In: Feingold KR, Anawalt B, Boyce A, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.; 2000-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279022/
2. Lorenz FJ, Tucker J, Milarachi EN, Hearn M, King TS, Goldenberg D. Hypocalcemia After Thyroidectomy in Patients with Prior Bariatric Surgery: A Propensity Score Matched Analysis from a National Administrative Database [published online ahead of print, 2022 Aug 22]. Thyroid. 2022;10.1089/thy.2022.0312. doi:10.1089/thy.2022.0312
3. Thyroidectomy in patients who have undergone gastric bypass surgery. Goldenberg D, Ferris RL, Shindo ML, Shaha A, Stack B, Tufano RP. Head Neck. 2018 Jun;40(6):1237-1244. doi: 10.1002/hed.25098. Epub 2018 Feb 8. PMID: 29417651