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Wednesday, 15 September, 1999, 18:11 GMT 19:11 UK
Sex hormone blamed for forgetfulness
Brain scan
The hormone oestrogen impacts on the brain
Feeling forgetful? Then blame it on your hormones.

Women's memory may in part be governed by the female sex hormone oestrogen, a scientist has discovered.

A Canadian expert has found that women deprived of oestrogen suffer memory lapses that vanish when the hormone is replaced

Dr Barbara Sherwin, of McGill University in Montreal, says the findings show that oestrogen has a beneficial impact on the parts of the female brain that control thinking.

Previous studies have suggested that mental ability is linked to oestrogen exposure in the womb.

There is also some evidence that hormone replacement therapy (HRT) protects the brains of postmenopausal women against degenerative diseases such as Alzheimer's.

However, little is known about how the hormone shapes the intellect of reproductively active women.

Dr Sherwin said attempts to monitor changes in cognitive performance throughout the menstrual cycle have proved inconclusive, possibly because oestrogen levels only fluctuate slightly and never fall below a certain threshold.

Now Dr Sherwin and her colleagues have followed a group of 100 women in their mid-forties, each of whom suffered a sudden drop in circulating levels of oestrogen after their ovaries and uterus had to be surgically removed.

The researchers divided the women into two groups, one of which received HRT after the operation, the other a placebo.

The women were shown pairs of unrelated words and subsequently had to recall the second of each pair when cued by the first word.

The women on HRT scored just as well as they had before their operation, but the placebo group performed significantly worse.

The women in the placebo group also noticed changes in their own behaviour.

They complained of not being able to remember things and of having to make lists, which they had never needed to do in the past.

Dr Sherwin said: "They weren't demented, they weren't losing their jobs or unable to function. Nonetheless it was a documentable decrease."

Uterine tumours

Dr Sherwin has also looked at a group of women in their early thirties who had uterine tumours.

Because the growth of these tumours is promoted by oestrogen, the women had been treated with a drug that suppressed production of the hormone.

After treatment, half the women were given HRT. The other half acted as controls.

Again, loss of oestrogen lowered the women's memory scores. Two months after treatment with the oestrogen suppresser had stopped, women given HRT were back to normal.

But the controls, whose oestrogen levels still had not returned to normal, showed the same memory deficit.

Bruce McEwen, a neuroendocrinologist at Rockefeller University in New York, said: "There are reversible cognitive deficits that are not of enormous magnitude, but enough to bother high-functioning women so that they should report them to their gynaecologist."

The research is reported in New Scientist magazine.

See also:

16 Jul 99 | Health
Hormones: the elixir of youth
27 Aug 99 | Health
HRT spray alternative
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