By the time men reach their 50s, about half will notice that their once-full head of hair is now thinning, according to Rogaine. Roughly one-third of the male population will suffer from male pattern baldness, which can start in a guy’s 20s, and many are willing to shell out significant amounts of money on products promising to restore their hair. Researchers at the University of California, Los Angeles, might have discovered one more treatment that could help those suffering from hair loss, and it works by activating stem cells in the hair follicle. 

To grow hair, the team experimented with hair follicle stem cells as they knew these cells were always present, but typically inactive except during a new hair cycle. However, through the study, researchers learned that hair stem cells metabolize differently than other cells found in the body. The stems cells in the hair follicle use glucose found in the bloodstream, to produce a metabolite known as pyruvate. Then, this new substance can either make its way to the mitochondria where it will make energy or be converted into lactate, another metabolite.

"Our observations about hair follicle stem cell metabolism prompted us to examine whether genetically diminishing the entry of pyruvate into the mitochondria would force hair follicle stem cells to make more lactate, and if that would activate the cells and grow hair more quickly," said study co-author Heather Christofk, associate professor of biological chemistry and molecular and medical pharmacology, in a statement on ScienceDaily.

So, in their study on mice, the scientists prevented lactate from being produced, halting stem cell activation. Then they increased lactate in mice, finding that this actually spurred hair growth by activating the stem cell.

"Before this, no one knew that increasing or decreasing the lactate would have an effect on hair follicle stem cells," said study co-author William Lowry, a professor of molecular, cell and developmental biology, in a statement. "Once we saw how altering lactate production in the mice influenced hair growth, it led us to look for potential drugs that could be applied to the skin and have the same effect."

Although the scientists did identify two drugs that may help with hair loss, they have not been tested for use in humans and are years away from being prescribed.

The new research also might help people diagnosed with alopecia, an autoimmune disease that causes baldness. Age and gender are not factors of the condition as anyone can develop it, though it often starts in adolescence.

About 6.8 million Americans have alopecia, according to the National Alopecia Areata Foundation. It starts when the immune systems attacks hair follicles, causing growth to slow, and maybe even stop. Each case varies, and some may have constant bouts of growth and loss, while others may regrow their hair normally. Currently, there is no cure, but the hair follicles in people with alopecia remain alive, meaning that growth can come back at any time. Doctors aren’t quite sure what triggers the condition, but some medications may be useful in regrowing hair.