(HealthDay News) -- Progesterone, a female sex hormone, may help treat traumatic brain injury (TBI), U.S. scientists report.

"We found encouraging evidence that progesterone is safe in the setting of TBI, with no evidence of side effects or serious harmful events," study author Dr. David Wright, an assistant professor in the department of emergency medicine at Emory University Health Sciences Center in Atlanta, said in a prepared statement.

His team conducted a phase II study of 100 patients with blunt TBI, which typically occurs in falls or in car and motorcycle crashes.

About 13 percent of TBI patients who received intravenous progesterone died within 30 days, compared to about 30 percent of patients who received a placebo. Most of the patients who died had severe TBI.

The findings were published online in the October issue of the Annals of Emergency Medicine.

"In addition, we found a 50 percent reduction in the rate of death in the progesterone-treated group. Furthermore, we found a significant improvement in the functional outcome and level of disability among patients who were enrolled with a moderate brain injury," Wright said.

The next step in this research is to confirm the findings of this study in a much larger group of TBI patients.

Widely known as a female "sex steroid," progesterone is also a neurosteroid that's critical for the normal development of neurons in the brain and "exerts protective effects on damaged brain tissue," the researchers wrote. Progesterone is naturally present in the brains of females and males.

More information

The U.S. National Institute of Neurological Disorders and Stroke has more about traumatic brain injury.