Dr. E. David Crawford of the University of Colorado Cancer Center said the production of androgens like testosterone depends on an intact system in which the brain recognizes hormone levels, signals the pituitary to increase or decrease production, and the pituitary in turn sets the testes in motion.
"By targeting the production of androgens by the testes, we could break that system at many other points," Crawford said in a statement. "For example, estrogen is similar enough to testosterone that administering estrogen to patients tricked the brain into thinking testosterone hormone levels were high -- with high presumed hormone levels, the brain sent no production signal to the pituitary. But estrogen therapy led to side effects including breast enlargement."
Another class of drugs -- luteinizing hormone releasing hormones -- intervened in this signaling chain at the level of the pituitary in a similar way to estrogen, but for those with bone metastasis in the back, spinal complications could occur, Crawford said.
However, androgen antagonists like the drug Enzalutamide -- currently in phase III clinical trials -- target cells' ability to trap testosterone that exists in the body, Crawford said.
"With this approach, it doesn't matter how much testosterone is floating around, as long as prostate cancer cells are unable to grab it," Crawford said.
The review was published in the British Journal of Urology International.