Natural testosterone refers to the testosterone naturally secreted by the body, which is mainly produced by the testicles and is regulated by positive and negative feedback of HPTA.
Exogenous testosterone refers to testosterone introduced into the body from the outside, including testosterone replacement therapy (TRT) or anabolic steroids (AAS).
Exogenous testosterone plays a role similar to natural testosterone, but it does not completely replace the role of natural testosterone.
When exogenous testosterone is introduced, it can increase overall testosterone levels, which brings various benefits such as improving the body's anabolism, increasing muscle mass, strength, and improved athletic performance. It can also relieve symptoms associated with low testosterone, such as fatigue, decreased libido, and mood changes.
However, exogenous testosterone does not fully replicate the complex hormone levels and regulation provided by naturally produced testosterone in the body. The body's naturally produced testosterone is subject to complex feedback loops and hormonal interactions that cannot be replicated by external testosterone management alone.

Exogenous Testosterone vs Natural Testosterone
Natural testosterone is continuously secreted into the circulatory system by testicular endocrine cells, and the concentration fluctuates little, showing a circadian rhythm. Exogenous testosterone is released by a one-time injection or orally, which can cause significant fluctuations in serum testosterone levels. Because of the different ways in which they are released, the ways in which exogenous testosterone and its metabolites bind to testosterone receptors also differ.
Natural testosterone interacts with aromatase or 5AR in the body to produce testosterone metabolites, and corresponding actions also occur in the body. Some exogenous testosterone is derived from testosterone, but the structure will change, and when it does not interact with aromatase or 5AR, it will also bring corresponding side effects.
Exogenous testosterone levels are not controlled by the endocrine system, and excessive use or absence of medical supervision during use can cause side effects including hormonal imbalance, cardiovascular, mood, and inhibition of natural testosterone production.