Diagnostic Imaging
April 2003

OVERREAD

PET unlocks hormones and pain

Women's hormones can influence how much or how little they feel pain, according to University of Michigan researchers. The finding could help unlock the workings of fibromyalgia and other disorders. The investigators used PET to study the mu-opioid neurotransmitter system, which the brain uses to naturally kill pain. In the double-blind placebo-controlled study, the scientists injected salt water into volunteers' masseter muscle to induce pain similar to that caused by temporomandibular joint disorders. They then used PET to scan the patients once during their early follicular phase and again during the same phase in another month, after the women had been wearing an estrogen-releasing skin patch.

When estrogen levels are high in women, the brain's m-opioid system responds more actively than when their estrogen is low, inceasing women's ability to release endorphins, the researchers suggested. The study was presented at the February meeting of the American Association for the Advancement of Science.