Thyroid cancer, central neck surgery and the incidental removal of parathyroid tissue raise the risk for hypoparathyroidism in children after total thyroid removal, according to a study.
Yet, the risk of permanent hypoparathyroidism is low.
The study, “Postoperative Hypoparathyroidism After Total Thyroidectomy in Children,” was published in the Journal of Surgical Research.
Surgery to remove the thyroid glands, called a thyroidectomy, can lead to hypoparathyroidism, which refers to low levels of the parathyroid hormone (PTH). In turn, the lack of PTH causes a strong decline in calcium, known as postoperative hypocalcemia, which is the most common complication of total thyroidectomy in children, leading to abnormal bone remodeling and a higher risk for fractures.
The probability of experiencing postoperative hypocalcemia and the associated risk factors are not completely understood.
Researchers from the University of California at San Francisco hypothesized that most children with postoperative hypocalcemia would regain normal parathyroid function by one year after the operation, and that children with thyroid cancer would be at higher risk for developing the condition, compared to children whose surgery was not related to cancer.
The team further reasoned that patients who needed central lymph node dissection (CLND), or removal, would be more likely to develop both transient and permanent postoperative hypoparathyroidism (needing calcium and vitamin D supplements for more than one year), because of the likelihood of disrupting parathyroid blood supply and unintentionally removing parathyroid tissue.
The scientists reviewed the records of patients younger than 21 who underwent total thyroidectomy from June 2012 to January 2019 at the university’s hospital.
Of 68 eligible patients (median age 15, 83.8% females), 17 had surgery due to cancer and 51 due to suspected benign thyroid disease, most commonly Graves’ disease.
Twenty-eight (41%) exhibited hypocalcemia following surgery, 11 of whom were symptomatic. These patients received both calcium and vitamin D supplements until the amount of calcium in their blood rose to at least 8 mg/dL.
Although eight of such patients (11.8%) required supplemental calcium and vitamin D for more than six months post-surgery, only two — both with biopsy-proven thyroid cancers — experienced permanent hypoparathyroidism.
Hypoparathyroidism lasted at least six months in five patients with thyroid cancer (29%), which compared to three cases (5.9%) among the group with benign disease.
Twelve of the patients diagnosed with thyroid cancer underwent CLND, with eight developing hypocalcemia while still in the hospital.
After surgery, the number of patients identified with cancer rose to 26. Seven (27%) required calcium and vitamin D supplementation for six months, compared to only one of the remaining 42 patients with benign findings.
Parathyroid tissue was found upon post-operative lab analysis in 14 patients (20.6%), meaning that some parathyroid tissue had been removed incidentally. Six of these patients, or 42.9%, required more than six months of calcium supplementation.
The incidence of long-term hypocalcemia after surgery among people with benign disease was low, with only one case of Graves’ disease having hypocalcemia at six months, but not at one year.
Overall, the main risk factors for hypoparathyroidism lasting at least six months were cancer, CLND, and the unintentional removal of parathyroid tissue.
“In our study population,” the team wrote, “for those children with postoperative hypocalcemia persisting at six months, the majority experienced complete resolution by one year. Permanent hypoparathyroidism in children after total thyroidectomy is uncommon.”
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