Figure 17: Where do Hormones Originate? Signals from the brain, (white arrow) stimulate the pituitary to release a substance (yellow arrow)
that in turn, causes the testes and ovaries to secrete the majority of the hormones testosterone and estrogen found in a person (blue and pink
arrows, respectively). The pituitary also stimulates the adrenal gland (green arrow) to secrete a small amount of estrogen and testosterone in both
sexes (pink and blue arrows, respectively). Some tumors, such as those originating in the breast and prostate, also secrete large amounts of the
hormones estrogen and progesterone (pink and blue arrows, respectively).
A New Day for Anti-hormone Therapy
Hormones like estrogen, progesterone, testosterone and their
derivatives influence the growth of certain subtypes of breast
cancer and most cancers of the male and female reproductive
organs (see Fig. 17). These hormones attach to specific proteins
called receptors, in a lock-and-key fashion, which stimulate cancer
growth and survival. This knowledge has provided insight into risk
factors and treatments for some of these hormone-fueled cancers.
In breast cancer, for example, understanding that estrogen drives
the approximately 70% of breast cancers that express the estrogen
receptor led to the clinical development of anti-estrogen therapies.
These drugs work in one of two ways. Some drugs, like tamoxifen,
attach to the estrogen receptors inside cancer cells, blocking
estrogen from attaching to the receptors. Other therapies, like
aromatase inhibitors, lower the level of estrogen in the body so that
the cancer cells cannot get the estrogen they need to grow. Anti-
estrogen therapies have been extremely successful, as indicated by
AACR Cancer Progress Report 2012