RESEARCH - Surging hormones blamed for pain

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Nature.com

Published online: 25 August 2005; | doi:10.1038/news050822-6

Surging hormones blamed for pain

Study of sex-change patients reveals role of oestrogen.

Carina Dennis

Women have long been known to experience more pain than men. And the idea

that sex hormones are to blame has just been bolstered by a study into pain

thresholds in a unique study group: people undergoing sex-change operations.

Men taking female hormones often start to experience chronic pain, says

Aloisi, a physiologist from the University of Siena in Italy. In a

study of 54 men taking oestrogen and anti-androgens as treatment to become

women, 30% reported developing pains, primarily chronic headaches, during

their treatment.

" We found that oestrogen in high amounts induced pain in these men, " says

Aloisi, who presented her work at the 11th World Congress on Pain in Sydney,

Australia, this week.

In another study of women taking testosterone to become men, says Aloisi,

more than half found their aches and pains improved. " They seemed to feel

better generally, " she adds.

The results back up previous research on sex differences in pain. Although

no one knows exactly how sex hormones affect pain tolerance, researchers

think testosterone dulls pain by muting the excitatory pain pathways in the

central nervous system, while oestrogen heightens pain by blocking the

inhibitory mechanisms that damp pain sensing.

The evidence for this is piling up. But the story about oestrogen is more

confusing than it first seemed, conference members heard.

Ups and downs

On the one hand, pain typically arises during the menstrual cycle when

oestrogen is at its lowest ebb, as during menstruation. On the other, girls

report more pain than boys from the onset of puberty when oestrogen starts

to surge.

It seems to be sudden changes in hormone levels that are the problem, rather

than the levels themselves, says LeResche, an epidemiologist from the

University of Washington, Seattle. " It is the withdrawal or fluctuation of

oestradiol that is associated with pain, " she says.

To check this theory, LeResche is starting to study women who choose to take

the contraceptive pill all the way through their cycle, so that they never

menstruate. LeResche will investigate whether keeping their oestrogen levels

up affects their experience of pain.

Managing pain

Researchers at the conference added that such findings should be taken into

account in pain management.

Serge Marchand of the University of Sherbrooke in Quebec, Canada, who has

studied testosterone levels in women with chronic pain, suggests that

clinicians should measure levels of sex hormones in patients. An imbalance

could be exacerbating their problems, he says.

And Aliosi advocates hormone replacement therapy in some chronic-pain

patients. She has started one trial that bolsters testosterone in male

patients with low levels of the hormone. She thinks this idea could also be

applied to women, although she adds that giving testosterone to women is

more complicated than giving it to men.

http://www.nature.com/news/2005/050822/full/050822-6.html

Not an MD

I'll tell you where to go!

Mayo Clinic in Rochester

http://www.mayoclinic.org/rochester

s Hopkins Medicine

http://www.hopkinsmedicine.org