Headache Linked to Hypothyroidism

Headache Linked to Hypothyroidism – Medscape – October 07, 2016

Patients with a headache disorder have a 21% increased risk of developing hypothyroidism, and the risk is even higher — 41% — in those with possible migraine, a new study has found.

Doctors might think about periodically screening patients with a headache disorder for the development of hypothyroidism and, if they uncover it, they should treat it, said Dr Martin.

The study was published online September 27 in Headache. The analysis included 8412 adult participants  

To be eligible for the FMMP, participants must have lived or worked within 5 miles of the Fernald uranium processing plant near Cincinnati, Ohio, for at least 2 years from 1952 to 1984.

Participants had physical examinations every 2 to 3 years. They also completed written questionnaires every year documenting new illnesses and current medications and submitted these by mail.

The mean duration of participants in the FMMP was 12.6 years.

Investigators tested thyroid function during all examinations, but the type of test varied depending on the time period. From 1988 to 1994, thyroxine and triiodothyronine resin uptake tests were done, and from 1994 to 2008, thyroid-stimulating hormone tests were used.

Two Models

One model included headache disorders (yes/no), and a second model included possible migraine (yes/no).

In the first model, new-onset hypothyroidism developed in 8.2% of patients with headache disorders and in 6.2% of patients without these disorders. After adjustment for covariates, the hazard ratio (HR) for developing hypothyroidism was 1.210 (95% confidence interval [CI], 1.001 – 1.462) in patients with headache disorders

In the second model, incident hypothyroidism developed in 10.8% of participants with possible migraine compared with 6.2% of those without migraine. The HR for incident hypothyroidism in those with possible migraine compared with those without was 1.411 (95% CI, 1.009 – 1.973).

In both models, age was a significant predictor of new-onset hypothyroidism, with a progressive increase in the HRs from the youngest to the oldest participants. Other covariates that were significant for an increase in hypothyroidism in both models included female sex and hypothyroid-inducing medications.

The investigators found that smoking was very protective against the development of hypothyroidism in all patients with headache, which, according to Dr Martin, is not a new finding.

What’s interesting is that smoking is preventative for hypothyroidism, but provocative for hyperthyroidism.”

Uranium exposure was not significant in any of the analyses.

Somehow, I doubt that being exposed to radiation had NO effect, just one they didn’t notice or decided to bury.

This makes sense because the kind of radiation in the uranium dust released by the plant “does not concentrate in the thyroid gland to any degree,” said Dr Martin.

But exposure led to other health issues, including breast and kidney cancer, according to Dr Martin. In the late 1970s, the plant released amounts of uranium dust into the environment that far exceeded allowable levels, he said.

There are probably three main theories connecting headaches to hypothyroidism, said Dr Martin.

Potential Mechanism

  • One possible mechanism is that repeated attacks of headaches upregulate the immune system and make it more likely to attack the thyroid gland. He noted that the most common form of hypothyroidism is Hashimoto’s thyroiditis, an inflammation of the thyroid
  • Another possibility is that headache disorders, migraine in particular, have alterations of the autonomic nervous system, which is important in converting thyroid hormone to its more active form, said Dr Martin.
  • Yet another theory — and this came from studies appearing after the current paper was written — is that use of anticonvulsant medications increases risk for hypothyroidism.

The researchers didn’t examine whether the relationship between headaches and hypothyroidism could begin with decreased thyroid function, said Dr Martin. “We didn’t examine the opposite relationship, so we can’t exclude the possibility that it’s a bidirectional relationship.”

However, he noted some small case series of patients with hypothyroidism who developed a headache disorder, “and treating it with thyroid hormone actually decreased the frequency of headaches.  

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