Abnormal secondary sex characteristics, such as hair pattern, can point to hormonal problems, which would mean the endocrine system is involved. A circulatory problem might be indicated by, for example, an aneurysm in the abdomen. Several laboratory tests can help diagnose impotence. Tests for systemic diseases include blood counts, urinalysis, lipid profile, and measurements of creatinine and liver enzymes. For cases of low sexual desire, measurement of testosterone in the blood can yield information about problems with the endocrine system.
Healthy men have involuntary erections during sleep.
If nocturnal erections do not occur, then the cause of impotence is likely to be physical rather than psychological. Tests of nocturnal erections are not completely reliable, however. Scientists have not standardized such tests and have not determined when they should be applied for best results. The man's sexual partner also may be interviewed to determine expectations and perceptions encountered during sexual intercourse. Most physicians suggest that treatments for impotence proceed along a path moving from least invasive to most invasive.