Posted on Aug 28, 2012, 6 a.m.
In both healthy adults and those with mild cognitive impairment, daily injections of growth hormone-releasing hormone (GHRH) improved cognition, including executive function.
Growth hormone-releasing hormone (GHRH), growth hormone (GH), and insulin-like growth factor 1 (IGF-1) exert potent effects on brain function, but their levels decrease with advancing age. Growth hormone-releasing hormone (GHRH) is key to the production of both GH and IGF-1. Previously, a number of studies suggest that elevating levels of these hormones in people at risk for cognitive impairment might prevent mental decline or improve function. Laura Baker, from the University of Washington School of Medicine (Washington, USA), and colleagues enrolled 152 adults, ages 55 to 87 years, including 66 with mild cognitive impairment (MCI). Subjects were randomly assigned to receive either daily subcutaneous injections of GHRH, or placebo. The primary outcome was cognitive change measured by a battery of standard tests at baseline and weeks 10, 20, and 30 (following a 10-week washout period). The researchers also conducted blood tests at those intervals to measure circulating levels of the three hormones, finding that GHRH increased insulin-like growth factor 1 levels by an average factor of 2.17 –within the normal physiological range. Those taking GHRH exhibit a significant improvement in overall cognition that was comparable among both healthy participants and those with MCI. Importantly, GHRH significantly improved executive function, and appeared to improve verbal memory as well. Further, GHRH also reduced body fat by 7.4% . Reporting that adverse events were mild, the study authors conclude that: "Twenty weeks of [growth hormone-releasing hormone] administration had favorable effects on cognition in both adults with [mild cognitive impairment] and healthy older adults. “
Laura D. Baker, Suzanne M. Barsness, Soo Borson, George R. Merriam, Seth D. Friedman, Suzanne Craft, Michael V. Vitiello. “Effects of Growth Hormone-Releasing Hormone on Cognitive Function in Adults With Mild Cognitive Impairment and Healthy Older Adults: Results of a Controlled Trial.” Arch Neurol, August 6, 2012.