Tuesday, February 16, 2010 » 11:48am

Australian scientists have isolated a cause of poor memory in otherwise healthy older men.

It relates to elevated levels of a particular sex hormone.

Luteinising hormone (LH), which is produced by the pituitary gland, controls the release of testosterone and men with higher levels of it were shown to perform poorer on memory tests.

The finding has implications for the search for a treatment for Alzheimer's disease, says lead researcher Zoe Hyde.

While previous studies had found elevated LH levels in men with Alzheimer's disease, her research was the first to find the effect also in healthy men.

'We know that testosterone acts on the brain in a number of ways but LH was thought to have no direct effect,' says Ms Hyde, from the Western Australian Centre for Health and Ageing.

'This study provides new insight into how hormones affect the brain and reveals a potential target for Alzheimer's disease drug therapies.

'However, more work is required before we can fully understand the role that LH plays in the brain.'

The memory curbing effects of LH was independent of an older man's testosterone levels.

LH also controls the release of oestrogen in women.

Ms Hyde's research was conducted as part of the major Health in Men Study, which has followed a group of 12,000 men aged 65 and over since 1996.

It is the largest study of ageing men in Australia, funded by the National Health and Medical Research Council of Australia (NHMRC).

The research is published in this month's issue of the Journal of Alzheimer's Disease

Bigpond news Australia.