Comorbid conditions are conditions that occur at the same time as but independently of each other. With Migraine disease, perhaps the most common comorbid condition is major depressive disorder (clinical depression). Approximately 47% of Migraineurs also experience major depressive disorder, but neither causes the other.
Comorbid conditions can have significant impact on effective treatment of the individual disorders. Thyroid diseases, including hypothyroidism, are among the conditions now know to often be comorbid with headaches and Migraines. A strong connection has been found between hypothyroidism and new daily persistent headache (NDPH) and chronic Migraine.
Researchers have concluded that comorbid conditions can affect each other in multiple ways including how they progress and the amount of time it takes to diagnose them and find effective treatments. In addition, it's been shown that comorbid conditions may play a role in headaches becoming and remaining daily or near-daily. In some cases the response of Migraine to treatment of even borderline hypothyroidism has been dramatic. Spierings theorized that, "An explanation of the benefit of the treatment, at least with regard to the Migraine aura, could lie in the decrease of cerebral excitability associated with the correction of hypothyroidism."
"Thyroid and other endocrine hormones can play a notable role in the development of headache and Migraine and in their failure to respond to treatment," stated Dr. John Claude Krusz. "People tend to look at only reproductive hormones when, in fact, the endocrine hormones can play such a significant role." Dr. Krusz recommends that headache and Migraine patients have blood work to check thyroid, cortisol, and other endocrine hormone levels. He also recommends that free T3 and free T4 be checked, saying that the standard TSH test, "doesn't tell the whole story."
Bigal et al concluded, "Subclinical (undetected) hypothyroidism may be associated with the development of new daily persistent headaches. Also, hypothyroidism may be associated to refractoriness to treatment in patients with primary (primary headaches are headaches that are not caused by another disease or condition) headaches, e.g. Migraine."