Researchers from the Perelman School of Medicine at the University of Pennsylvania claim they have made the first steps towards what is arguably the holy grail for millions of men worldwide - a cure for baldness.
The scientists say they have found what causes baldness, giving hope that they can now find a way of stopping it.
Researchers analysed human and animal models and found that an abnormal amount of a protein called prostaglandin D2 caused baldness.
The researchers found that levels of PGD2 were three times greater in bald pates than that found in more hirsute heads.
"Although a different prostaglandin was known to increase hair growth, our findings were unexpected as prostaglandins haven't been thought about in relation to hair loss, yet it made sense that there was an inhibitor of hair growth, based on our earlier work looking at hair follicle stem cells," said George Cotsarelis, professor of dermatology at Perelman.
Researchers are trying to develop a treatment that could prevent baldness.