PTH Levels Help Predict Recovery 6 Months After Thyroid Surgery

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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Late recovery — longer than six months — from post-surgery hypoparathyroidism is not uncommon, and having levels of parathyroid hormone (PTH) within the normal range may indicate whether patients are more likely to recover, a study found.

“PTH is a useful biomarker in predicting long-term recovery of parathyroid function,” the researchers wrote, adding, “The chances of recovery are high (~50%) in patients with PTH [at normal levels] at 6 months” post-surgery.

Such patients often are able to be weaned from necessary, long-term, post-surgery supplementation with calcium/activated vitamin D, the team noted.

The study, “Parathyroid hormone of ≥1.6 pmol/L at 6 months is associated with recovery in ‘long term’ post-surgical hypoparathyroidism,” was published in the European Thyroid Journal.

Hypoparathyroidism occurs when there is not enough PTH in the body. This hormone is made by the parathyroid glands and helps keep the blood levels of calcium, phosphorus, and vitamin D within a normal range. Vitamin D and these two minerals are critical for bone health and for the proper functioning of many bodily systems.

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Patients with hypoparathyroidism have hypocalcemia — low blood levels of calcium — and hyperphosphatemia, which means they have high blood levels of a phosphorus-containing molecule called phosphate.

The most common cause of hypoparathyroidism is an injury to or the removal of all four parathyroid glands, or parts of them, during surgery. This can happen accidentally during thyroidectomy, which is a surgery to remove all or part of the thyroid gland.

Hypocalcemia develops the day after thyroidectomy in up to 60% of patients. While this is a transient effect for most individuals (about 90%), resolving within weeks or months, it may persist for six months or longer for other patients.

Beyond six months, hypoparathyroidism had been considered “chronic” or “permanent,” the researchers noted.

Treatment for the condition involves calcium and vitamin D supplements, and its goal is to keep patients free of symptoms in the first few weeks. After this period, they are weaned off the supplements, unless hypoparathyroidism persists for six months or more and the patients are considered unlikely to recover.

However, recent studies have shown recovery beyond this mark.

Now, a team of researchers set out to determine how many patients take more than six months to recover from post-surgery hypoparathyroidism, and what may predict this late recovery.

They looked back at the records of patients who underwent thyroidectomy between 2009 and 2018 at a teaching hospital in the U.K.

Patients were identified as having hypoparathyroidism if they met one or more of the following criteria on the day after surgery: low PTH levels (less than 1.6 picomol/L), low adjusted calcium levels (less than 2.1 mmol/L), or the start of treatment with a calcium or vitamin D supplement.

Of the 911 patients in this study who underwent thyroidectomy, 270 (29.6%) developed hypoparathyroidism. Most patients (79.6%) were women and their median age was 45.2 years.

A total of 192 (21.1%) were started on supplements. Of these, 138 (71.9%) saw their parathyroid function return to normal within six months. The remaining 54 (28.1%) were still on supplements at that half-year mark. These individuals made up 5.9% of all patients in the study, which is in line with the reported 6% of patients who develop persistent post-surgery hypoparathyroidism in the U.K.

Among the 54 patients with hypoparathyroidism at six months, 19 (35.2%) were weaned off supplements and achieved recovery at a median of 1.3 years. The remaining 35 (64.8%) still had hypoparathyroidism at a median 3.4 years after thyroidectomy.

To find out what may predict late recovery, the researchers watched for differences between patients who did and did not show a later recuperation. There was no difference in age, sex, indication for surgery, and type of surgery between the two groups.

However, “adjusted calcium and especially PTH at or beyond six months was significantly higher in patients with recovery of function,” the researchers wrote.

All of those who recovered had a PTH level of 1.6 picomol/L or greater compared with 16 (64.0%) of the 25 patients who had yet to recover, the data showed.

“If the PTH level at or after 6 months is within normal range, then there is almost 50% likelihood of recovery in the ensuing three years,” the researchers wrote.

“This makes PTH a useful biomarker in clinical practice as these patients can be actively tried to wean off the supplements,” they said.

While most of the patients who recovered did so within the first three years after thyroidectomy, the longest recovery time was around five years.

Recovery from post-surgery hypoparathyroidism “is a dynamic process and can occur even after 6 months, and in some cases, several years after surgery,” the researchers concluded.