This can be thought of in the following way: the hypothalamus in the human brain has a detection mechanism which regulates the release of many hormones which control the production of androgens by the testes and the adrenal glands. If this detection mechanism detects an abnormally high amount of androgen / anabolic steroids, which it recognises primarily as testosterone, then the hormones responsible for testosterone release will have their production decreased, and so the testes etc. will no longer be stimulated by these hormones, and so will cease, or decrease, production of natural testosterone, and so cause testicular shrinkage.
NOT NECESSARILY TRUE . Faced with an unnatural rise in estrogen, some steroid users will then take a class of drugs called aromatase inhibitors , which are designed to block the production of estrogen in women with breast cancer, Weinerman says. That's right: It's a breast cancer drug. And aside from the obvious danger in further messing with hormones, guys who turn to aromatase inhibitors can have side effects like joint and muscle pain, the loss of sex drive, and the loss of bone density, which can then result in osteoporosis, according to a Susan G. Komen Foundation report .