A once-a-day pill helped completely rebuild bone in rodents with severe osteoporosis, a finding that could lead to a new class of drugs to treat the brittle-bone disease in humans, US researchers said.

The team tested a compound that blocks the production of serotonin produced in the gut in mice and rats with a severe form of the disease and found they completely recovered their bone density.

“If you break the bone, it looks like a normal bone,” said Dr Gerard Karsenty, of Columbia University Medical Centre in New York, whose study appears in the journal ‘Nature Medicine’.

Using the findings, he said the team is working to develop this type of treatment for human patients with osteoporosis, in which bones become fragile and porous, increasing the risk of fracture.

“There is an urgent need to identify new, safe therapies that can increase bone formation on a long-term basis,” Karsenty said.

The study builds on prior research by the same team that found the chemical messenger serotonin - when released by the gut - inhibits bone formation.

Serotonin is most commonly known for its role in the brain as a chemical messenger but 95 per cent of the serotonin in the body is produced in the gut as a way to regulate bone formation, Karsenty said.

“We thought that if we could inhibit the synthesis of serotonin in the gut, it could be a way to treat osteoporosis,” he said.

“Luckily for us, there are a couple of inhibitors of gut-derived serotonin that do not affect the synthesis of brain-derived serotonin.”

But Karsenty added the findings were very preliminary and more tests needed to be done before the drug can be tested in people with osteoporosis