Testosterone replacement therapy may help elderly men with mild Alzheimer's disease, research suggests.
Testosterone is known to affect mood
A University of California, Los Angeles team found hormone doses significantly improved quality of life for Alzheimer's patients.
Carers reported improvements in energy levels, physical health and interpersonal relationships - but not in memory or other mental skills.
Details are published in the journal Archives of Neurology.
Lead researcher Dr Po Lu said: "The results suggest that testosterone replacement therapy holds potential for improving quality of life of Alzheimer patients and merits further testing with a larger group of patients and with a longer treatment period."
The UCLA team compared 16 men with mild Alzheimer's with 22 healthy men over a 24-week study.
All the volunteers were given a daily skin patch containing a gel which either contained testosterone or no active medication.
Male ageing is associated with a gradual decline in testosterone level.
This has been linked to decreased libido, mood alterations and changes in the way we think, as well as physical changes such as decreased muscle strength and a greater risk of osteoporosis.
Previous research has also found significantly lower concentrations of testosterone in middle-aged and elderly men who developed Alzheimer's disease.
Harriet Millward, of the Alzheimer's Research Trust, said a number of studies had hinted that testosterone replacement therapy might have positive effects on mood or mental processes.
However, she said a recent review of over 40 studies concluded it had only very limited effects in men over 65.
"This research studied only a small number of people over a relatively short period, and therefore has largely inconclusive results.
"More research is needed before we can assess whether testosterone therapy could benefit men with Alzheimer's disease."
Dr Susanne Sorensen, of the Alzheimer's Society, agreed.
"As there is currently no cure, and a limited number of treatment options for people with Alzheimer's disease, every promising treatment avenue deserves to be followed up," she said.