People with chronic migraines who overuse pain relievers may have abnormalities in certain hormonal responses, a small study suggests.

It's known that overusing migraine medications can sometimes cause periodic migraines to become chronic, and the new findings suggest that altered hormone regulation may be one reason, the study's lead author, Dr. Innocenzo Rainero stated.

Migraines are usually episodic attacks of head pain, often accompanied by nausea and sensitivity to light and sound. Chronic migraine is diagnosed when people suffer attacks at least 15 days a month for more than three months.

Though it's not clear why migraines sometimes become chronic, medication overuse has been considered a risk factor.

In addition, lab research has shown that the drugs used to treat migraine attacks -- including certain non-steroidal anti-inflammatory drugs ( NSAIDs), ergot alkaloids and triptans -- may change the body's secretion of hormones such as growth hormone and the stress hormone cortisol.

Knowing this, Rainero and his colleagues at the University of Turin in Italy tested several hormonal responses in 18 adults with chronic migraine and 18 healthy comparison subjects.

All of the migraine sufferers were overusing some medication, most often NSAIDs. But none was taking any of the drugs used to prevent migraine attacks.

To test study participants' hormonal function, the researchers injected them with specific "releasing" hormones that trigger the secretion of growth hormone, cortisol, thyroid-stimulating hormone and adrenocorticotropic hormone.

The results are published in the medical journal Headache. Compared with healthy adults, chronic migraine sufferers showed either reduced or heightened secretion of three of these hormones.

According to the researchers, this appears to be the first study to test these hormonal responses in people with chronic migraine and medication overuse, and it's not clear that medication abuse is responsible for the altered hormonal function.

Migraine itself involves a "chronic stress condition," the researchers note, and could have impaired hormonal activity in the study patients.

However, Rainero said, the findings do strengthen the belief that abuse of anti-migraine drugs is a "serious medical condition." They also support the use of preventive medications, he added, as these drugs may head off both migraine attacks and overuse of migraine-relieving medications.

SOURCE: Headache, April 2006.