Specific Thyroid Surgery Procedures Dictate Later Risk of Hypoparathyroidism

Joana Carvalho, PhD avatar

by Joana Carvalho, PhD |

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The specific surgical procedures used when patients undergo thyroid surgery —  known as thyroidectomy — dictate the risks they have of developing hypoparathyroidism and other complications, a study found.

Because this type of surgery is associated with a high risk of complications and requires specialized care, it should only be performed by experienced surgeons, the investigators said.

The study, “Complications after medullary thyroid carcinoma surgery: multicentre study of the SQRTPA and EUROCRINE databases,” conducted by researchers in Sweden and Germany, was published in the British Journal of Surgery.

Thyroid removal is the standard procedure for patients with medullary thyroid carcinoma (MTC), a form of thyroid cancer that is estimated to affect nearly 0.5 per 100,000 people. Yet, the scientists said that clinicians should first weigh its benefits in treating cancer against the risk of surgical complications.

Hypoparathyroidism, in which low levels of the parathyroid hormone (PTH) lead to a decrease in blood calcium levels, is one of the possible complications of this type of surgery. The condition occurs when the parathyroid glands that normally produce PTH are damaged during surgery. In addition, patients are at risk of recurrent laryngeal nerve (RLN) palsy, a condition in which the nerves serving the vocal cords are damaged.
Although population-based studies have reported the incidence of these surgery complications, they did not focus on the factors that might increase the risks of patients developing either RLN palsy or hypoparathyroidism, the researchers said.
“Analysis of these factors is pivotal for adequate preoperative patient counselling and decision‐making regarding the extent of surgery,” they wrote.
The researchers have now reported the findings of a study that assessed the clinical outcomes, and identified the factors, that might increase the risks of both of these complications in people with MTC who underwent thyroid surgery.
The study was based on data from 650 patients — 245 men and 405 women, with a median age of 56 — who had surgery in 69 different centers between January 2004 and September 2019.
Two large European online databases, the Scandinavian Quality Register for Thyroid, Parathyroid and Adrenal Surgery (SQRTPA) and the EUROCRINE database, were used to identify these patients.

Hypoparathyroidism and RLN palsy were considered at least temporary in the cases in which patients were still on medication at a second follow-up visit or at a first follow-up appointment without subsequent data. Statistical analyses were used to determine potential risk factors for surgical complications that were at least temporary.

Among the patients analyzed, 170 (26.2%) developed hypoparathyroidism. In turn, among the 451 patients who underwent laryngoscopy after surgery, 62 (13.7%) had at least temporary RLN palsy. A total of 17 people (2.6%) experienced bleeding that required reoperation after having thyroid surgery.

The analyses found that patients who had central lymph node dissection (CLND) during surgery had a 2.2 times higher risk of developing hypoparathyroidism after the procedure. This risk increased further, to 2.78 times, when CLND was accompanied by unilateral lateral lymph node dissection (LLND). With CLND and bilateral LLND, the risk climbed to 2.83 times higher. In addition, the team found that patients in whom four or more parathyroid glands had been identified during surgery had a 4.18 times higher risk of developing at least temporary hypoparathyroidism.
Notably, CLND and LLND are surgical procedures in which the lymph nodes located on the center, or lateral, portions of the neck are removed during thyroid surgery. In the case of LLND, lymph nodes may be only removed from one side (unilateral) or both sides (bilateral) of the neck.
As for RLN palsy, individuals who had both CLND and LLND had a 4.04 times higher risk of developing this complication following surgery. In turn, those who had T4 tumors — tumors growing past the thyroid gland — had a 12.16 times higher risk of having RLN palsy.
“Complications after surgery for MTC are procedure‐specific and may relate to the unavoidable consequences of radical dissection needed in some patients,” the researchers wrote. They noted that the more extensive and invasive these procedures are, the more likely it is for patients to develop complications.
The results also demonstrated that nearly half (46.2%) of the patients showed no signs of cancer spreading to nearby lymph nodes (N0 disease), indicating that in all these cases lymph node removal during thyroid surgery was unnecessary.“The high rate of N0 disease after lymph node dissection underscores the need for adequate patient counselling, and the need for improved prognostic factors that can be used to select patients for more extensive surgery,” the investigators wrote.
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About the Author

Joana Carvalho, PhD avatar
Joana Carvalho, PhD Joana holds a bachelor’s in biology, a Master of Science in evolutionary and developmental biology, and a PhD in biomedical sciences from Universidade de Lisboa, Portugal. Her work has been focused on the impact of non-canonical Wnt signaling in the collective behavior of endothelial cells — those that make up the lining of blood vessels — found in the umbilical cord of newborns. In addition to several research fellowships, she was awarded two Erasmus scholarships to conduct part of her studies in France.

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complications, medullary thyroid carcinoma, MTC, recurrent laryngeal nerve palsy, thyroid surgery

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