The injectable form of the parathyroid hormone is a liquid that has to be refrigerated, but for the implantable device, the researchers developed a powered version that remains effective when sealed in its tiny compartment for as long as a year.

The device itself can be implanted in a doctor's office with local anesthetic.

Farra and his colleagues say safety tests of a small, 20-dose prototype unit were successful, and they are now designing a 365-dose version.

"We anticipate two years to complete the design, and then we may be required to do two additional trials, taking us out to a total of four years before the device is available on the commercial scale."

The price of the device is speculative, but Farra says the cost should be similar to the current regimen of daily injections.