Clinical Presentation and Symptom Clusters
The manifestations of testosterone deficiency vary significantly depending on the age of onset. If the deficiency occurs during fetal development, it may result in ambiguous genitalia or undescended testes. During puberty, a lack of testosterone leads to a failure to develop secondary sexual characteristics, such as muscle mass, a deep voice, and body hair, often resulting in "eunuchoid" body proportions where the arms and legs grow out of proportion to the trunk.
In adult men, the symptoms are often more subtle and can be grouped into sexual and non-sexual clusters. The most specific "red flag" symptoms include a significant drop in libido, a decrease in the frequency of spontaneous morning erections, and erectile dysfunction. Non-sexual symptoms, while less specific, often include persistent fatigue, a depressed or irritable mood, and a decrease in physical vigor. Over several years, untreated hypogonadism can lead to metabolic changes such as increased visceral fat, the development of breast tissue (gynecomastia), and a significant reduction in bone mineral density, which increases the risk of fragility fractures.