6-OXO, also known as androstenetrione, is a "suicidal estrogen inhibitor" described and created by Illinois chemist Patrick Arnold. Arnold may be best known for creating "THC," a formerly undetectable anabolic steroid sold to BALCO Labs and allegedly taken by several Major League Baseball star players.

Marketed as a dietary supplement, 6-OXO functions by binding to estrogen and permanently deactivating it. Arnold notes that this results in increased testosterone levels and decreased estrogen levels. This was confirmed by a study in the Journal of the International Society of Sports Nutrition. The independent researchers found that 6-OXO "significantly increased free testosterone, dihydrotestosterone, and testosterone/estrogen ratios in healthy males."

6-OXO, like most compounds that can affect hormone levels, does have potential side effects for healthy males. Females should not take 6-OXO.

6-OXO is designed to lower estrogen levels, thereby increasing testosterone levels. While not life- threatening, prolonged low estrogen levels can produce side effects for males. This is why Patrick Arnold suggests on the label that 6-OXO should be not used more than eight weeks.

A study led by Dr. Adrian Dobs, a professor of medicine and oncology at Johns Hopkins School of Medicine, found a link between low estrogen levels and low bone mineral density. Of the 1,220 men who participated, "Men with lower estradiol levels, lower free testosterone levels, and higher circulating SHBG concentrations were more likely to have low BMD," the study found.

Prolonged low estrogen levels can also result in a decrease in sex drive, increased susceptibility to joint or tendon injuries, fatigue, memory lapses, increase in cholesterol and night sweats.

Another possible side effect of 6-OXO is acne or oily skin. David Tolson, a biochemistry researcher, reports in Iron Magazine the most common side effect of 6-OXO is acne. Increases in testosterone and DHT or changing hormonal levels can result in acne on the shoulders and back. Acne can result in short-term use as well as prolonged use.

Prolonged use of 6-OXO can increase the risk of BPH, or benign prostatic hyperplasia. This is typical of any compound that raises DHT levels. Excess DHT can bind to the prostate and cause it to swell. This is another reason why use beyond eight weeks is discouraged. Prostate enlargement is a serious condition but was not observed in the eight-week study of 6-OXO reported in the Journal of the International Society of Sports Nutrition.

There is a risk of hair loss for users of 6-OXO who are prone to male pattern baldness. As it does regarding BPH, excess DHT can attach to hair follicles susceptible to androgenic alopecia and shrink them--which results in hair thinning. Dr. William Rassman, medical director and founder of the New Hair Institute, confirms this. He states that increase testosterone levels can lead to miniaturization in hair follicles.