Growth hormone might increase life span

DALLAS, July 1 (UPI) -- A U.S. study has linked growth hormone to starvation in what scientists say might be a clue to increasing life span and developing diabetes treatments.

University of Texas Southwestern Medical Center researchers used genetically altered mice in the study that found the actions of growth hormone are blocked during fasting by a fat-burning hormone called FGF21.

Growth hormone has many functions, the scientists said, such as controlling the length of developing arm and leg bones in children. But it also, among other things, increases levels of IGF-1, a hormone that promotes growth. Too much growth hormone can cause insulin resistance, resulting in diabetes.

In the study, mice genetically altered to produce excess FGF21 grew to be much smaller than ordinary mice, although they ate more and had more fat in proportion to their size. Paradoxically, the altered, smaller mice produced much greater amounts of growth hormone than normal.

"In addition, intermittent fasting -- which increases FGF21 concentrations -- also extends life span in mice," said Professor Steven Kliewer, senior author of the study. "This raises the intriguing possibility that FGF21 might be a longevity factor."

The study is reported in the journal Cell Metabolism.