People who have migraines or other headache disorders may be at greater risk for developing hypothyroidism, according to a study published online September 27, 2016 in Headache: The Journal of Head and Face Pain. But the researchers have yet to discover how the two disorders are related to one another.
“Our study is one of the largest studies published to date suggesting that headache disorders are a risk factor for the future development of hypothyroidism,” explained lead author Andrew Martin, a fourth-year medical student at the University of Cincinnati (UC) College of Medicine, in Cincinnati, OH.
Other studies have found that headache disorders are associated with hypothyroidism, but these studies were unable to conclude whether headache disorders raise the risk of hypothyroidism or vice versa.
For this investigation, UC researchers performed a longitudinal retrospective study using data from 8,412 adults who participated in the Fernald Medical Monitoring Program (FMMP), a medical surveillance program of residents who live near the Fernald uranium processing plant outside of Cincinnati. (Although radiation is a known risk factor for developing hypothyroidism, the researchers found no association between uranium exposure and thyroid disease in this study.)
About 26% of subjects reported headache disorders, and approximately 7% developed new onset hypothyroidism. The researchers determined that headache disorders preceded the development of hypothyroidism.
“Our study found that patients with preexisting headache disorders had a 21% increased risk of developing new onset hypothyroidism while those with possible migraine showed an increased risk of 41%,” the authors wrote. The latter finding may indicate that people with migraine are particularly susceptible to hypothyroidism, the researchers noted.
The results also showed that female gender, increasing age, obesity, and hypothyroid-inducing medications are associated with new onset hypothyroidism.
Several proposed mechanisms might explain the association between headache disorders and hypothyroidism, the authors noted. Headache disorders and/or migraine might affect the immune system, which could lead to Hashimoto’s thyroiditis. Another possibility is that sympathetic nervous system activity in migraine patients may cause changes that affect the thyroid gland. Shared genetic mechanisms or environmental factors could play a role, too.
“It is possible that the development of hypothyroidism in a headache patient might further increase the frequency of headache, as past studies have found that treatment of hypothyroidism reduces the frequency of headache,” said corresponding author Vincent Martin, MD, Professor of Medicine in the UC Department of Internal Medicine and Co-director of the Headache and Facial Pain Center at the UC Gardner Neuroscience Institute.
"Regardless, physicians should be more vigilant in testing for hypothyroidism in persons with headache disorders,” Dr. Martin advised.