Study Identifies Risk Factors for Hypoparathyroidism in Children After Thyroid Removal

Removal of lymph nodes in the neck and invasion of neighboring tissues with thyroid cancer cells are risk factors for developing hypoparathyroidism following total thyroidectomy in children, a study reports.

The study, “Risks of Hypoparathyroidism After Total Thyroidectomy in Children: A 21-Year Experience in a High-Volume Cancer Center,” was published in the World Journal of Surgery.

Hypoparathyroidism is characterized by abnormally low levels of parathyroid hormone (PTH), which is key for regulating a person’s calcium and phosphorus levels. The disorder is estimated to affect 20% of patients who undergo thyroidectomy (surgery to remove the thyroid gland), with the risk being higher among children.

The factors underlying the risk of hypoparathyroidism after total thyroidectomy are unknown.

Researchers at MD Anderson Cancer Center in Texas collected data from 184 children who underwent the procedure between January 1997 and September 2018.

The majority of those (111) had the surgery because of suspected or proven thyroid cancer. In 106 cases, cancer was confirmed after surgery, with most of those (103) having papillary thyroid cancer.

The remaining 73 children underwent surgery due to inherited mutations in the RET gene, a known cause of thyroid cancer. Thirty-three of these children had already developed cancer.

Overall, 67 children (36.4%) developed hypoparathyroidism, 33 of whom with PTH levels under 2 pg/mL, 26 with PTH under 10 pg/mL and receiving calcitriol on hospital discharge, and eight also given calcitriol based on calcium levels alone.

Hypocalcemia, or low levels of calcium in the blood, is a common complication following thyroidectomy. Calcitriol, a vitamin D analog, is given to to treat and prevent low levels of calcium and bone disease.

Hypoparathyroidism was temporary in 61 children, with a median recovery time of 48 days. Eleven children took six months or more to recover.

Six patients developed permanent hypoparathyroidism by the end of follow-up, which lasted as long as 5,221 days (slightly more than 14 years).

The researchers also assessed the incidence of hypoparathyroidism in relation to surgical procedures and disease features.

A statistical analysis revealed that central neck dissection, a procedure to remove lymph nodes within the central in thyroid cancer cases, and gross extrathyroidal extension — when the tumor spreads into thyroid-surrounding tissues — were associated with a more than four-fold greater risk of post-surgery hypoparathyroidism.

The study identified “central neck dissection and the presence of gross extrathyroidal extension as two independent risk factors for postoperative hypoparathyroidism in pediatric patients,” the researchers wrote. Both surgeons and “clinicians involved in postoperative care should also be mindful of the risk of hypoparathyroidism in such patients and routinely dedicate care to postoperative PTH and calcium monitoring and replacement,” they said.