For more than 80 years, men have been told that testosterone helps prostate cancer grow. But a very different picture has emerged over the past two decades.

The prostate is a small gland that sits just below the bladder. Its job is to produce the fluid that helps transport sperm, and it relies heavily on testosterone to do so. In fact, the prostate is one of the body parts most affected by testosterone.

All prostate cells, whether healthy or cancerous, contain androgen receptors. These are the molecular switches that initiate testosterone’s action inside cells. When testosterone binds to these receptors, it helps the prostate grow and function normally.

This close hormonal control is important, but it also sets the stage for one of the most enduring assumptions in men’s health: because testosterone stimulates normal prostate growth, it must also stimulate cancer growth.

This belief rested largely on the Nobel prize-winning research of Charles Huggins in the 1940s. He found that prostate cancer shrank when testosterone levels were lowered and accelerated when testosterone was added, via injections.

Lowering testosterone levels, known as androgen deprivation therapy, became the standard treatment for advanced prostate cancer. It still is. Removing testosterone often shrinks tumours, slows disease progression and improves survival.

This belief became........

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