Testosterone production is best understood as a three part process. Three sites in the body for three processes, is an even better way to look at it.
As with most important processes, the first site is in the brain. The hypothalamus, specifically. It releases a hormone called gonadotropin-releasing hormone (GnRH), which acts on the anterior pituitary gland.
The anterior pituitary gland is the second site in this process, because in response to the GnRH it releases luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
Third site, the testicles, where in response to LH and FSH, testosterone is produced.Learn more about the role of testosterone