 It has been found that very low levels of androgens, as in castration, are able to significantly stimulate growth of prostate cancer cells and accelerate disease progression.Although castration ceases production of androgens by the gonads and reduces circulating testosterone levels by about 95%, low levels of androgens continue to be produced by the adrenal glands, and this accounts for the residual levels of circulating testosterone.Moreover, it has been found that prostate gland levels of , which is the major androgen in the prostate, remain at 40 to 50% of their initial values following castration.