Hypothalamic-Pituitary-Testicular-Axis (HPTA): The Hypothalamus, Pituitary, and Testicles are the main sources of endogenous testosterone production.

Suppress – Decrease natural testosterone production

Shut down – Completely stop natural testosterone production

Testosterone – Testosterone is necessary for other functions in the human body other than muscular and cellular development. Without it, one could potentially have problems sexually, mentally, and physically. The body has a system called the LH feedback loop. The more androgenic hormones that you have in your body, the less your body will feel the need to produce any testosterone at all. Basically, the point is Testosterone is necessary in almost any cycle, except a short DHT cycle (which will be explained later). 19nors should never be taken without test. This also illustrates why PCT is necessary.