Scientists uncover new hormone in unusual discovery

Scientists just discovered a hormone that may solve a long-standing biological mystery. 

It's difficult to prove you've identified a new hormone — a chemical signal that directs behavior in distant cells, often by Traveling through the bloodstream. To be sure, you need to confirm where it's made, which tissues it affects and that it can be found in the bloodstream, senior study author Holly Ingraham, a professor and vice-chair of cellular and molecular pharmacology at the University of California, San Francisco, told Live Science.

"Most have been discovered, so it's pretty novel to actually uncover a new hormone," said Dr. Sundeep Khosla, a physician-scientist at Mayo Clinic in Rochester, Minnesota, who was not involved in the research. "They make a pretty convincing case that this is really a hormone."

Scientists had previously found the substance in mammals, including humans, Khosla noted, but they didn't know it was a hormone. The new study shows that the chemical — which the researchers have dubbed "maternal brain hormone" — travels from the brain to bone-forming cells, where it helps build bone, according to the new study, published Wednesday (July 10) in the journal Nature.

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This bone-building comes into play after pregnancy, when estrogen levels plummet and the demand for calcium skyrockets as the body starts making milk. Normally, estrogen strengthens bones and prevents their calcium from being stripped away. Thus, it's been unclear how bones retain much of their strength during breastfeeding and then recover soon after weaning.

The new hormone "adds an important piece to that whole biology that we didn't know before," Khosla told Live Science. What's more, although it's important in the postpartum period, the new hormone can also boost bone growth in males, the researchers showed.