A new study published in the Journal of Endocrinological Investigation suggests that vitamin D status below 20 ng/ml may be an independent risk factor for predicting failure of radioiodine therapy among patients with Graves’ disease.
Graves’ disease (GD) is an autoimmune disease that causes the thyroid gland to become hyperactive, resulting in a condition known as hyperthyroidism. Hyperthyroidism is characterized by the overproduction of thyroid hormones.
Since the thyroid affects many different aspects of health, signs and symptoms of GD can be wide-ranging. These symptoms can include anxiety and irritability, tremor of the hands or fingers, thick red skin usually on the shins or tops of the feet, weight loss, changes in sexual functioning, and bulging eyes.
GD is considered a common condition, affecting more than 3 million people in the U.S., affecting approximately 5 times as many women as it does men.
There are three options for the treatment of GD: anti-thyroid drugs (ATDs), thyroidectomy, and radioiodine therapy (RIT). RIT is the easiest and least expensive treatment with the fewest side effects, which has caused it to become one of the more popular methods. However, treatment failure may occur in 8-50% of cases after the first dose of RIT.
Previous studies have found that patients with GD had lower vitamin D levels compared to patients without GD. Therefore, researchers wanted to determine whether vitamin D levels could predict prognosis in RIT.
The researchers compared the vitamin D levels between 128 patients with GD who received RIT to 60 healthy participants. They also analyzed the success of the treatment. Here is what they found:
- Healthy participants had significantly higher vitamin D levels than GD patients (p < 0.001).
- RIT was successful in 96 (75%) of GD patients and failed in 32 (25%).
- Vitamin D levels were significantly lower in patients who failed in therapy (p < 0.001).
- Patients with vitamin D levels below 20 ng/ml were 8.83 times more at risk for failure of RIT than those with vitamin D levels of 20 ng/ml or higher (p < 0.001).
The researchers concluded,
“Overall, serum 25(OH) D < 20 ng/ml might be an independent risk factor for predicting failure of RIT in GD patients.”
The study is limited by its study design, which prevents the researchers from making any statements of causality. Additionally, the small sample size limits its generalizability.
Further trials should investigate whether vitamin D supplementation reduces the risk of RIT failure for patients with GD.