Just one cigarette blocks estrogen production in women’s brains

VIENNA, Austria — Just one cigarette blocks estrogen production in a woman’s brain, a new study reveals. The discovery may explain why women often find it harder than men to quit the habit.

“For the first time, we can see that nicotine works to shuts down the estrogen production mechanism in the brain of women,” says Associate Professor Erika Comasco of Uppsala University in a media release.

“We were surprised to see that this effect could be seen even with a single dose of nicotine, equivalent to just one cigarette, showing how powerful the effects of smoking are on a woman’s brain,” Comasco continues.

“This is a newly-discovered effect, and it’s still preliminary work. We’re still not sure what the behavioral or cognitive outcomes are; only that nicotine acts on this area of the brain, however we note that the affected brain system is a target for addictive drugs, such as nicotine.”

The researchers worked with 10 healthy female volunteers who were each given a dose of nicotine — similar to the amount in one cigarette. Researchers then injected the volunteers with a radioactive tracer that attached to a molecule in the body that binds to aromatase, the enzyme that produces estrogen.

Using MRI and PET brain scans, scientists were able to see the amount of estrogen in the body and identify where it was in the brain. The results showed that the single dose of nicotine moderately reduced the amount of aromatase in the brain, meaning there was less estrogen after just one cigarette.

This is the first time that this relationship has been discovered in humans. Scientists have yet to investigate the effect of one cigarette on a man’s brain and hormones.

Aromatase (estrogen synthetase) detected in the thalamus (red spot).
Aromatase (estrogen synthetase) detected in the thalamus (red spot).

One cigarette ‘has a significant impact on the brain’

“This discovery leads us to believe that nicotine’s effect on estrogen production has a significant impact on the brain, but perhaps also on other functions, such as the reproductive system – we don’t know that yet,” Professor Comasco says.

“There are significant differences in the way men and women react to smoking. Women seem to be more resistant to nicotine replacement therapy, they experience more relapses, show greater vulnerability for heritability of smoking, and are at greater risk of developing primary smoking-related illnesses, such as lung cancer and heart attacks. We need now to understand if this action of nicotine on the hormonal system is involved in any of these reactions.”

“Of course this is a comparatively small group of women, we need a larger sample to confirm these findings. Nevertheless, the message is that nicotine has various effects on the brain, including on the production of sex hormones such as estrogen,” Comasco adds.

“This is indeed an important first finding. Smoking has many adverse effects in men and in women, but this particular effect of nicotine on the reduction of estrogen production in woman was not known before, says Professor Wim van den Brink, Emeritus Professor of Psychiatry and Addiction from the Academic Medical Center at the University of Amsterdam, who did not take part in the research.

“It should be noted, however, that tobacco addiction is a complex disorder with many contributing factors. It’s unlikely that this specific effect of nicotine on the thalamus (and the production of estrogen) explains all the observed differences in the development, treatment and outcomes between male and female smokers. It is still a long way from a nicotine induced reduction in estrogen production to a reduced risk of nicotine addiction and negative effects of treatment and relapse in female cigarette smokers, but this work merits further investigation.”

Researchers presented the findings at the European College of Neuropsychopharmacology Congress in Vienna, Austria.

South West News Service writer Alice Clifford contributed to this report.

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