German researchers have discovered that women with high levels of oestrogen in their blood look unusually young for their age.

The researchers, from the University of Erlangen, estimated the age of 100 women aged between 35 and 55, and then measured the level of the female hormone oestrogen in their blood.

They found that in some cases women with high levels of oestrogen appeared to be eight years younger than they really were. In contrast, a lack of oestrogen added up to eight years to a women's appearance.

Professor Ludwig Wildt and Dr Teresa Sir-Petermann were following up previous studies suggesting an association in both humans and animals between female attractiveness and fertility.

Fertility link

Scientists believe that oestrogen acts to make a woman look more attractive so that she increases her chance of getting pregnant.

Fertility is linked to oestrogen and reduces as levels of the hormone diminish when a woman approaches the menopause.

But the age at which this occurs varies considerably between different individuals.

The researchers found they consistently overestimated the age of low oestrogen women and underestimated those with high levels of the hormone.

Writing in the Lancet medical journal they said: "The discrepancy between estimated and real age could be as high as eight years in either direction.

"These data suggest that serum oestrogen concentrations have a pronounced impact on the estimation of age and, by inference, on the estimation of reproductive competence made by an independent observer."

Professor Wildt and Dr Sir-Petermann did not try to explain how oestrogen made women look younger.

However, they said it was known that hormone replacement with oestrogen after the menopause increased skin thickness and quality.