Muscle loss or muscle wasting is one of the late signs of prolonged low testosterone levels. Before muscle loss, your body becomes weaker and less energetic for a long time.
Muscle cells contain androgen receptors for testosterone. Muscle fibers are preserved when testosterone is attached to these receptors. When testosterone levels become low, muscle maintenance stops and muscle wasting starts.
Also, studies show that low testosterone increases fat deposition, especially in the abdomen and chest areas. The fat cells in these areas produce aromatase, an enzyme that converts testosterone into estrogen. Estrogen then increases fat deposits in other areas of the body. It becomes a vicious cycle. The more the fat deposits are, the lower the testosterone becomes over time. Other symptoms such as depression, fatigue, hair loss, and low sex drive may appear earlier.