Hormone therapy 'can shrink brain'
Updated on 12 January 2009
Common forms of hormone replacement therapy (HRT) can shrink the brains of post-menopausal women, research has shown.
The discovery may explain earlier findings associating HRT with an increased risk of memory loss and dementia, experts believe.
US researchers carried out brain scans on 1,400 women aged 71 to 89 who had participated in a major HRT trial one to four years previously. They found women who had been on HRT had smaller brain volumes in two key areas than those given an inactive "dummy" placebo.
Brain volume was 2.37 cubic centimetres lower in the frontal lobe and 0.10 cubic centimetres lower in the hippocampus. Both areas of the brain are involved in thinking and memory skills, and hippocampus shrinkage a known risk factor for dementia.
Study leader Dr Susan Resnick, from the National Institute on Ageing in Baltimore, Maryland, said: "These effects were most apparent in women who may already have had some memory problems before they started taking hormones. This suggests that oestrogen may adversely affect thinking skills among women whose brains may already be beginning a neurodegenerative disease process."
The women had all taken part in the Women's Health Initiative trial, a landmark American study which highlighted a link between long-term HRT and increased stroke risk.
It been thought that higher numbers of "silent strokes" and brain injuries might account for declining memory and thinking skills in HRT users. But this was ruled out by a second study reported today which showed HRT was not associated with damage caused by loss of blood flow to the brain.
"This was not what we expected to find", said lead author Dr Laura Coker, from Wake Forest University in Winston-Salem, New Carolina.
Both studies, which involved the same participants, were published today in the journal Neurology.
Dr Resnick said: "Our findings suggest that hormone therapy in older post-menopausal women has a negative effect on brain structures important in maintaining normal memory functioning. However, this negative effect was most pronounced in women who already may have had some memory problems before using hormone therapy, suggesting that the therapy may have accelerated a neurodegenerative disease process that had already begun."
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