Hypocalcemia and Magnesium Disorders After Thyroidectomy

Disorders of magnesium metabolism may be a modifiable target in reducing the incidence of hypocalcemia after total thyroidectomy, according to new findings published in JAMA Otolaryngology - Head and Neck Surgery.

Researchers arrived at their conclusion after performing a cross-sectional analysis of 126,766 commercially insured patients younger than age 65 years who underwent total thyroidectomy between January 1, 2010, and December 31, 2012.

The results of the study indicated that risk factors for short- and long-term hypocalcemia included female sex, age younger than 40 years, having a diagnosis of thyroiditis or cancer, vitamin D deficiency, concurrent neck dissection, intraoperative parathyroid or recurrent laryngeal nerve injury, and magnesium disorders.

Notably, magnesium disorders were found to be associated with the highest likelihood of postoperative hypocalcemia at 30 days and at 1 year, and were also associated with greater health care costs. Now, according to the researchers, further research is warranted to assess the benefits of perioperative magnesium supplementation in this patient population.

Endocrinology Consultant discussed the potential implications of these findings further with study author Jonathon O. Russell, MD, director of Endoscopic and Robotic Thyroid and Parathyroid Surgery and assistant professor of Otolaryngology - Head and Neck Surgery at Johns Hopkins Medicine in Baltimore, Maryland.

Endocrinology Consultant: In your study, you and your colleagues said that, to date, there has been no large database study examining the factors associated with and consequences of long-term hypocalcemia in patients after thyroidectomy. What does your study add to the literature in this regard?

Dr Russell: This study demonstrates an association between hypomagnesemia and hypocalcemia in patients who have undergone thyroidectomy. In other words, patients who had thyroid surgery and are hypomagnesemic are more likely to have hypocalcemia as well. It is not clear that this is causal, but this association is interesting.

Endocrinology Consultant: How might these findings aid in risk stratification for hypocalcemia after total thyroidectomy?

Dr Russell: Currently, these findings do not change our management. Future studies will be needed to determine if all patients should be screened for low magnesium levels before surgery.

Endocrinology Consultant: How might the finding that magnesium disorders are a potentially modifiable risk factor for postoperative hypocalcemia impact hospitalizations and health care costs?

Dr Russell: Postoperative hypocalcemia is one of the most morbid complications of thyroid surgery. While it is rare, the costs are staggering because of how common thyroid surgery is. If we are able to decrease the incidence of hypocalcemia to any degree, it could have a significant impact on health care costs.

Endocrinology Consultant: How might these findings affect future recommendations for prophylaxis against postthyroidectomy hypocalcemia, especially in terms of supplementation? What future research needs to be done to reach the point where perioperative magnesium supplementation might be recommended in this patient population?

Dr Russell: My colleagues and I are in the process of establishing a study evaluating the randomized prophylactic administration of magnesium to patients undergoing total thyroidectomy. If we can demonstrate that this administration effectively reduces postoperative hypocalcemia, it would significantly change the current management of these patients.

Endocrinology Consultant: What clinical takeaways do you hope endocrinologists, endocrine surgeons, and related clinicians learn from this study?

Dr Russell: In patients who have postoperative hypocalcemia, magnesium disorders should be corrected as needed. Future studies may demonstrate further benefits for the use of magnesium supplementation.

—Christina Vogt

Liu RH, Razavi CR, Chang HY, et al. Association of hypocalcemia and magnesium disorders with thyroidectomy in commercially insured patients [Published January 9, 2020]. JAMA Otolaryngol Head Neck Surg. doi:10.1001/jamaoto.2019.4193.