BACKGROUND
Surgery to remove all, or part, the thyroid gland is commonly needed to treat some types of thyroid disease. One problem that can happen after thyroid surgery is development of low calcium levels due to damage to the parathyroid glands. The parathyroid glands are four very small structures (each about the size of a grain of rice) that live in the neck on the surface of the thyroid gland. Their job is to make a single hormone (parathyroid hormone), which works with vitamin D in the body to control a person’s calcium levels. When calcium levels are low, parathyroid hormone levels are increased to help increase calcium levels.

It is critical that the parathyroid glands work normally after thyroid surgery. If they do not, which can happen if the parathyroid glands are damaged, removed or irritated during surgery, calcium levels will be too low. This can cause serious side effects, including severe muscle cramps and seizures. For this reason, understanding how best to preserve parathyroid gland function after thyroid surgery is very important.

The research described here studied people who had surgery to remove all, or part, of their thyroid to learn if low vitamin D levels before thyroid surgery increases the risk of low parathyroid hormone levels after surgery.

THE FULL ARTICLE TITLE
Vaitsi K et al 2021 Pre-operative vitamin D deficiency is a risk factor for post-thyroidectomy hypoparathyroidism: A systematic review and meta-analysis of observational studies. J Clin Endocrinol Metab. Epub 2021 Jan 23:dgab039. PMID: 33484571.

SUMMARY OF THE STUDY
In order to better understand the possible effect of low vitamin D levels on parathyroid gland function after thyroid surgery, the authors of this study collected information published between 2009 and 2020 on the relationship between parathyroid gland activity, thyroid surgery and vitamin D levels. They then used mathematical testing (statistics) to see if low vitamin D levels before thyroid surgery increased the risk that the parathyroid glands would not work well after surgery (hypoparathyroidism, or low parathyroid hormone levels).

Overall, the authors included 755,585 people who underwent thyroid surgery. They found that mild or moderately low vitamin D levels before thyroid surgery increased the risk of temporary (lasting less than 6 months) low parathyroid hormone levels after thyroid removal. If very low vitamin D levels were present before thyroid surgery, patients also had an increased risk of having permanent low parathyroid hormone levels after surgery.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
The study authors found that low vitamin D levels before thyroid surgery increased the risk that the parathyroid glands would not work well after surgery, which could cause significant health problems. For this reason, the authors suggest that people who are planning to undergo thyroid surgery should have their vitamin D levels checked and, if these levels are low, should take a vitamin D supplement before surgery. This might decrease the risk of having a low parathyroid hormone level, and associated side effects, after thyroid surgery.

— Jason D. Prescott, MD PhD

Table of Contents | PDF File for Saving and Printing