Hypoparathyroidism After Thyroid Removal Found to Surpass Estimates
Surgeons urged to preserve parathyroid function when removing thyroids
Persistent hypoparathyroidism after complete removal of the thyroid gland is more common than previously thought, a study in Japan has found.
These findings, based on health insurance claims, add to previous reports linking persistent hypoparathyroidism after the surgery (called a total thyroidectomy) with greater risk for renal insufficiency and cardiovascular complications. “Therefore, surgeons should be more careful in preserving the parathyroid glands during total thyroidectomy,” the researchers wrote.
The study, “Actual prevalence of hypoparathyroidism after total thyroidectomy: a health insurance claims-database study,” was published in the journal Endocrine.
Hypoparathyroidism is characterized by abnormally low levels of the parathyroid hormone — a vital regulator of calcium and phosphorus levels in the body. It can develop from the damage caused during surgical removal of the thyroid and may require lifelong treatment with active vitamin D and calcium supplements.
The condition can be temporary or permanent. Current reports estimate that post-surgical hypoparathyroidism is temporary in 19% to 38% of cases, but permanent in up to 3% of cases.
However, scientists now believe that the rate of persistent hypoparathyroidism may be higher than currently recognized. Reasons for this include inconsistent definitions of post-surgical hypoparathyroidism across different studies and different policies about the use of active vitamin D and calcium supplements.
In the study, a team of researchers in Japan set out to estimate the actual rate of persistent hypoparathyroidism and the factors that predict its occurrence.
The researchers reviewed patient data collected by Japan Medical Data Center, which collects data from health insurance companies. The study included records from 2009 to 2019 of 2,388 adult patients. Persistent hypoparathyroidism was defined as receiving active vitamin D supplement prescriptions for more than one year after surgery and being diagnosed with hypoparathyroidism, postsurgical hypoparathyroidism, or low calcium levels after surgery.
Of the 2,388 patients identified, 73.4% of them were women, and the mean age was 45. Most patients (65.7%) had undergone thyroid surgery due to malignant cancer. Others had undergone surgery because of non-cancerous thyroid disease, the immune system disorder Graves’ disease, or a combination of Graves’ disease and cancer.
Active vitamin D supplements were prescribed to 61.4% of patients within a month of their surgery. A total of 484 patients (20.3%) were still prescribed these supplements one year and up two years after their surgery. However, after accounting for patients who were taking active vitamin D for osteoporosis (weak, fragile bones) and kidney failure, the researchers estimated the minimum persistent hypoparathyroidism rate to be 15.0%, with a maximum of 20.3%.
Notably, malignant thyroid tumor was found to be the only significant risk factor for persistent hypoparathyroidism.
“It is important to be aware that parathyroid function is not preserved after total thyroidectomy as previously recognized,” the investigators wrote. “It is crucial to promote research on techniques that allow any surgeon to easily preserve parathyroid gland function without relying on experience and skills.”