From the article:
In order to investigate testosterone’s role in the development of Alzheimer’s disease, the team took away the ability of male mice to produce testosterone. Some mice were then given a form of testosterone while others were given none.
The mice with lowered testosterone showed increases in levels of the protein beta-amyloid, which has been widely implicated as playing a role in the development of Alzheimer’s disease. They also showed signs of behavioral impairment.
The mice that were given testosterone showed reduced accumulation of beta-amyloid and less behavioral impairment.