Vitamin D May Reduce Rate of Hypoparathyroidism After Thyroid Surgery

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by Diana Campelo Delgado |

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Vitamin D supplementation before total thyroid removal may reduce the frequency of permanent hypoparathyroidism after surgery, a clinical study suggests.

However, as the difference compared with placebo was not statistically significant, future studies with more patients, more regular follow-ups, and biochemical results are needed to better understand this interaction, researchers said.

The study, “Post-Operative Permanent Hypoparathyroidism and Preoperative Vitamin D Prophylaxis,” was published in the Journal of Clinical Medicine.

Surgery to completely remove the thyroid gland, called total thyroidectomy, can lead to unintentional damage to the parathyroid glands and to hypoparathyroidism — meaning low levels of the parathyroid hormone (PTH). In turn, low PTH is associated with hypocalcemia, or calcium deficiency.

Researchers in Australia investigated whether high-dose vitamin D supplementation before surgery could decrease the incidence of permanent hypoparathyroidism, defined as needing activated vitamin D six months after surgery. Notably, vitamin D plays a vital role in intestinal calcium absorption and, if at normal levels, may lead to less severe symptoms of hypoparathyroidism.

The team also examined whether measuring PTH levels one day after surgery could help predict permanent hypoparathyroidism.

“Predicting permanent hypoparathyroidism through early identification of patients that require monitoring would allow early intervention to prevent severe hypoparathyroidism requiring in-patient care,” the scientists wrote.

The study included patients previously enrolled in the Vitamin D in Thyroidectomy (VIDIT) study, a trial evaluating the role of high-dose supplementation with vitamin D3 (cholecalciferol) in preventing hypocalcemia after surgery. No positive results were seen six months after thyroidectomy, although a subsequent analysis did find reductions in hypocalcemia and length of hospital stay.

Data were analyzed from 150 patients who underwent surgery at John Hunter Hospital and Newcastle Private Hospital for goiter (46.9%), Graves’ disease (30%), or thyroid cancer (23.1%) from August 2014 to December 2017. While goiter is an abnormal enlargement of the thyroid gland, Graves’ disease is an immune system condition characterized by overproduction of thyroid hormones.

From the total group, 20 patients (13.3%) were not available for a telephone questionnaire six months after surgery.

Participants included in the analysis had a mean age of 54.5 years, and were mostly women (76.7%). They were randomly assigned to receive either vitamin D3 (57 patients) or a placebo (73 patients).

Results showed that permanent hypoparathyroidism occurred in 11 patients (8.5%), three in the vitamin D group (5.3%), and eight in the placebo group (11%). Although the rate of permanent hypoparathyroidism in the vitamin D group was lower, the difference between groups was not considered statistically significant.

Of these 11 patients, six developed hypocalcemia (54.5%) over the six months of follow-up. Dosage of activated vitamin D ranged from 0.25 to 1 micrograms daily, with no significant differences between the treatment and placebo groups. Other factors such as surgical indication, sex, age, or body mass index (a measure of body fat) were not significantly associated with vitamin D dosage.

In addition, a statistical analysis showed no significant association between pre-operative supplementation with vitamin D3 and the incidence of permanent hypoparathyroidism after surgery.

The researchers then divided patients into two groups according to their PTH levels one day after surgery: either less than 10 picograms/ml, or equal to or above 10 picograms/ml. Statistical analysis showed no relationship between patients’ PTH levels and the incidence of permanent hypoparathyroidism.

Among the study’s limitations were the fact that the definition used for permanent hypoparathyroidism did not consider clinical features, biochemistry results, or calcium supplementation.

“A lower rate of permanent hypoparathyroidism was observed in the group taking high-dose preoperative cholecalciferol, however this was not statistically significant. Additionally, despite day 1 PTH being a reliable predictor in transient hypoparathyroidism, it did not predict permanent hypoparathyroidism,” the researchers concluded.