Hormones are naturally occurring substances secreted by specialised cells and circulated throughout the body in the blood. Hormones act by binding to receptors on the surface of and influencing the metabolism or behaviour of cells. The normal growth and development of a range of tissues throughout the human body occurs under the influence of hormones.
Excessive hormonal stimulation of cell proliferation increases the risk of mutation and subsequent proliferation of clones of mutated cells. Hormones are therefore capable of acting as powerful carcinogens, and are considered a 'complete carcinogen' because of their ability to both initiate and promote the development of cancers.4, 6, 7, 19
Hormones have been implicated in the genesis of breast, prostate, uterine, ovarian, testicular, thyroid and bone cancers. Increased exposure to the hormones oestrogen and progesterone in females has been demonstrated to increase the risk of breast cancer. The early onset of menstruation, late first pregnancy, obesity, late menopause and the use of oral contraceptives all increase the exposure of breast tissue to oestrogen, stimulating increased proliferation. Similarly, the male sex hormone testosterone has been implicated in the development of prostate cancer.6, 7, 19, 23
Access a current text and summarise the role of hormones in the development of the following cancers: