But light doses of dioxins can be beneficial for prostate

Nov 28, 2006 15:16 GMT  ·  By

Dioxins are toxic halogenated (usually with chlorine) organic compounds that affect the immune system, teeth and respiratory systems amongst others. Main sources of dioxins are herbicides, plastics, resins and bleaches. Dioxins can persist in the fat tissue of the body for several decades.

Now, scientists have discovered that high blood levels of dioxins may be linked with lowered testosterone levels and a not necessarily beneficial limitation of prostate growth, thus disturbing male endocrine and reproductive systems.

Dioxins enter the human organism mainly through the fatty meats, milk and dairy products. Levels of the dioxin TCDD (the main component of the herbicide Agent Orange) were measured in 964 veterans of Operation Ranch Hand when during the Vietnam War were sprayed herbicides.

A comparison group comprised 1,259 veterans who served during the same time period, 1962-1971, but not involved in the spraying program and thus exposed to dioxins levels equivalent to the general population. The veterans were tested during six examination cycles. The first cycle was initiated in 1982, so the veterans were monitored for more than 20 years. "Until now, we did not have very good evidence whether or not dioxins affect the human reproductive system," said Dr. Amit Gupta, a urologist at University of Texas, Southwestern Medical Center.

But "each increase in dioxin decreases the rate of benign prostate enlargement and decreases serum levels of testosterone." The findings in the Ranch Hand group were unclear. Low levels of TCDD were beneficial for the risk of prostate enlargement, but high levels did not stop prostate enlargement, a phenomena called hormesis. "Now we know that there is a link between dioxins and the human prostate leading us to speculate that dioxins might be decreasing the growth of the prostate in humans like they do in animals."

The benign prostate hyperplasia (BPH) is a human condition caused by an enlargement of the prostate. Patients must strain to pass urine and they also must urinate frequently, which can trigger complications like inability to urinate and urinary tract infection, sometimes with surgery necessary. "We found that the risk of developing BPH decreased with increasing exposure to dioxins in the comparison group," said Dr. Arnold Schecter, professor of environmental sciences at the UT School of Public Health Regional Campus.

"The risk of developing BPH was 24 % lower in the group with the highest dioxin levels compared to the group with the lowest levels. In the Ranch Hand group, the risk of BPH tended to decrease with increased exposure to dioxins, but at extremely high exposure levels there was a tendency for the risk to increase."

"It is known that lower testosterone levels are associated with decreased sexual function, decreased muscle mass and strength, infertility, increased fatigue, depression and reduced bone density," said Gupta. "What we found was that testosterone decreased, but we can't say that dioxin caused particular effects."

Additional studies of the impact of dioxins and other toxins on the male reproductive system are required. "Dioxins are toxic chemicals and will cause harmful effects in many other areas of the body."said Gupta. "We know that dioxin causes many endocrine disturbances in the human body. The study indirectly proves that BPH is an endocrine disorder." said Dr. Claus Roehrborn, professor and chairman of urology at UT Southwestern.

"It may be construed that a decrease in the risk of BPH is not a harmful effect, but the larger picture is that dioxins are affecting the normal growth and development of the reproductive system. Moreover, several effective treatments are available for BPH and thus reduction of BPH by a toxic compound is not a desirable effect." explained Gupta.

In the last decades, the world experienced a rise of male reproductive disorders: a decrease in sperm production by almost 50 %, three- to four times more testicular cancer cases, an increase in the incidence of cryptorchidism (when testes do not descend in the scrotum and get sterile) and hypospadias (abnormality of the urethra). This increase may be triggered by environmental contaminates that have endocrine-disrupting effects.