WEDNESDAY, March 29, 2006 (HealthDay News) -- The brain's hippocampus produces its own store of growth hormone, researchers report.
The finding could have implications for athletes taking growth hormone and metabolic steroids to increase muscle mass and for menopausal women using estrogen replacement therapy.
"Growth hormone has been associated with growth of muscles and bones, and the production of it was believed to lie mainly in the pituitary gland," study co-author Ken S. Kosik, co-director of the Neuroscience Research Center at the University of California, Santa Barbara, said in a prepared statement.
"No one had thought too much about what growth hormone might be doing in the brain. Hormones in the brain may not be obvious compared to what they are doing in the rest of the body," Kosik said.
The study, published in this week's Proceedings of the National Academy of Sciences, also found that women produce more growth hormone than men, that adults produce more than children, and that hormone production increases in response to estrogen. Differences in the amount of growth hormone in the brain may affect reasoning and mood, the scientists said.
The study authors previously found that production of growth hormone in the hippocampus increases with learning. The new study found that stress increases production, particularly in males. The effect of stress in females depends on how much estrogen they have at the time.
"One interesting interpretation of these results is that exposure to a stressful event increases growth hormone expression in males -- but the increase in females may be dependent on their levels of estrogen at the time," study first author Christine P. Donahue, instructor in the department of neurology at Harvard Medical School, said in a prepared statement.
More information
The Endocrine Society has more about growth hormone.
