Ralph Martins, a professor of Alzheimer's and Ageing at Edith Cowan University, said research found that men with lower levels of testosterone had higher levels of beta amyloid protein linked to Alzheimer's.
Beta amyloid protein is a toxic substance that can kill neurones in areas of the brain that are important for learning and memory, and is widely thought to lead to Alzheimer's.
"On the other hand, higher levels of testosterone coincide with lower levels of beta amyloid protein and improved cognitive performance," Martins told the annual meeting of the Australian Neuroscience Society in Perth on Monday.
Researchers are undertaking a clinical trial among men to determine if testosterone replacement could improve cognitive performance in men whose levels of the hormone had fallen due to ageing or treatment for prostate cancer.
Medicines can bring temporary
relief but no lasting cure
"Over the past 12 months, we have also been looking at another hormone, known as Luteinizing hormone, or LH, which acts to regulate testosterone and oestrogen levels," Martins said.
"We do not fully understand the role of this hormone but it has become clear that it also acts on brain cells."
Research over the past 10 years suggested falling levels of oestrogen in women of menopausal age also resulted in higher levels of the toxic protein beta amyloid, but the research so far was less conclusive than that among men.
"Animal studies are very conclusive in terms of increased beta amyloid protein coinciding with depleted levels of oestrogen in females," he said.
"We do not fully understand the role of this hormone but it has become clear that it also acts on brain cells"
Edith Cowan University, Australia
But he said clinical trials in the US had produced disappointing, inconclusive results.
The disease - first identified in 1906 by Alois Alzheimer - causes loss of memory, decline of cerebral function and the decline of personality.
Although drugs can temporarily improve memory there are at the moment no treatments that can stop or reverse the degenerative process.