An "abnormal" amount of a protein causes male pattern baldness, researchers at the University of Pennsylvania have discovered.
The protein, called prostaglandin D2, is found in the bald spots of the scalp of men who are losing their hair and inhibits hair growth.
The researchers at the Perelman School of Medicine said knowing what causes male pattern baldness could lead to new treatments.
The study says male pattern baldness affects 80% of men under 70 years old.
Prostaglandins play roles in other bodily functions, such as controlling cell growth and constricting and dilating smooth muscle tissue. A different prostaglandin, F2alpha, is known to increase hair growth.
The school released the study Wednesday. It was published in the Journal of Clinical Investigation.
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