Testosterone effects on cognition in health and disease.

Low testosterone is associated with many physical complaints as well as cognitive complaints. This article reviews the neurobiologic connection between gonadal steroids and cognitive functions, and mechanisms by which T may be considered neuroprotective. Studies of hormone replacement therapy in hypogonadal men as well as older men with late-onset hypogonadism (LOH) are reviewed as well as epidemiological studies of endogenous hormones and cognition. Studies examining T treatment in men with memory disorders such as Alzheimer's disease (AD) will also be reviewed. Some but not all studies of androgen replacement therapy in hypogonadal younger men, older men with LOH and AD patients suggest a potential beneficial effect on cognition, however a recent study indicated a negative effect. Most studies to date have been small and need further replication with randomized controlled studies using larger sample sizes with specific consideration of treatment risk factors.