New York, Jan 9 (IANS): In a surprising paradox, the male hormone testosterone, generally thought to be a feeder of prostate cancer, has been found to suppress some advanced prostate cancers.

The scientists at the Johns Hopkins University's Kimmel Cancer Centre also said testosterone therapy may also reverse resistance to testosterone-blocking drugs used to treat prostate cancer.

"These results suggest that testosterone therapy has the potential to reverse the resistance that eventually develops to testosterone-blocking drugs like enzalutamide," they noted.

In men whose prostate cancer spreads, doctors typically prescribe drugs that block testosterone production, but cancer cells eventually become resistant to this means of reducing the hormone.

For the study, the researchers enrolled 16 men who had been receiving testosterone-lowering treatment for metastatic prostate cancer.

The men were given three 28-day cycles of an intramuscular injection of testosterone and two weeks of a chemotherapy drug called etoposide.

Men who showed decreases in the levels of prostate specific antigen (PSA), a blood marker for prostate cancer, after three cycles were continued on testosterone injections alone.

"However, men should not try to self-medicate their cancers with testosterone supplements available over the counter," warned medical oncologist Samuel Denmeade, who led the small yet significant study of 16 patients with metastatic prostate cancer.

The study appeared in the journal Science Translational Medicine.