1 in 5 Graves’ disease patients have post-surgical hypoparathyroidism

Most patients recover in less than 6 months after thyroid removal

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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An illustration of a patient on a gurney headed to an operating room.

About one in five people with Graves’ disease who undergo a thyroidectomy, which is the surgical removal of all or part of the thyroid gland, develop hypoparathyroidism, but most recover in less than six months.

That’s according to a study looking back at the medical records of 216 people with Graves’ disease, an autoimmune disorder that makes the thyroid overactive.

Researchers also observed that women were at higher risk than men for developing hypoparathyroidism after surgery.

“Postoperative hypoparathyroidism can be caused by various factors,” researchers wrote. But “only the female sex proved to be a risk predictor,” they added.

The study, “Outcomes of Surgical Treatment for Graves’ Disease: A Single-Center Experience of 216 Cases,” was published in the Journal of Clinical Medicine.

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Graves’ disease occurs when immune system mistakenly attacks thyroid

Graves’ disease occurs when the immune system mistakenly attacks the thyroid and causes it to become overly active and make too much thyroid hormone. When this happens, it’s called hyperthyroidism. It can cause a number of symptoms, from weight loss to a rapid heartbeat and irritability.

While Graves’ disease can usually be treated with anti-thyroid medications or radioactive iodine to help bring down the production of thyroid hormone, a total or near-total thyroidectomy may sometimes be recommended.

The surgery is recommended for patients who can’t take anti-thyroid medications or those who have a thyroid tumor or severe Graves’ disease.

Like any surgery, a thyroidectomy carries certain risks and complications. One is accidental injury to or removal of the parathyroid glands, which can result in hypoparathyroidism, or too little parathyroid hormone (PTH) being made.

The parathyroid glands are four small glands located in the neck near the thyroid. They help regulate the amount of calcium in the blood by making PTH. When there is too little PTH, the amount of calcium in the blood drops and causes a range of symptoms. 

To find out how common it is for a thyroidectomy to result in hypoparathyroidism among people with Graves’ disease, a team of researchers in China reviewed the data of 182 women and 34 men who had the surgery at some point from 2013 to 2020. The mean age of the patients was 43.9 years.

Before the thyroidectomy, 211 (97.7%) had been on anti-thyroid medications and 23 (10.6%) had received treatment with radioactive iodine. For most (91.7%), this helped fully control the symptoms of hyperthyroidism.

Three-quarters (75%) had a total thyroidectomy, and the remaining had either a near-total (23.6%) or subtotal (1.4%) thyroidectomy. Subtotal thyroidectomy spares more tissue than near-total thyroidectomy with the goal of preserving part of the thyroid’s function.

The most common reason why patients were offered surgery was because they didn’t respond well to treatment with anti-thyroid medications (52.3%), followed by suspicion of a thyroid tumor (45.8%). After their thyroidectomy, patients stayed in the hospital for a mean 3.02 days. In 25 (11.6%), it was found that the parathyroid glands had been accidentally removed.

Almost half (48.1%) were diagnosed with a thyroid tumor. In 75 (72.1%), the tumor wasn’t bigger than one centimeter in diameter but in 48 (46.2%), it had spread to nearby lymph nodes.

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Postoperative hypoparathyroidism, voice hoarseness were transient in most cases

Sometimes during a thyroidectomy, the nerve that controls the vocal cords is damaged accidentally. After surgery, 24 patients (11.1%) experienced hoarseness and 15 (6.9%) had a transient paralysis of the vocal cords. Three (1.4%) had a permanent paralysis of the vocal cords, which means that the paralysis lasted for more than six months.

There were 45 (20.8%) cases of hypoparathyroidism after a total or near-total thyroidectomy; 42 (19.4%) recovered under calcium supplementation, with blood serum PTH and calcium returning back to normal levels within six months. 

“In most cases, the postoperative hypoparathyroidism and hoarseness were transient,” the researchers wrote.

Being male was found to reduce the risk of developing hypoparathyroidism after a thyroidectomy. The odds ratio was 0.22, that is, for every 22 men who develop hypoparathyroidism, there’ll be 100 women who also develop hypoparathyroidism after a thyroidectomy.