Previous studies on mice had shown that a hormone called insulin-like growth factor-1 helped reduce the accumulation of plaque on the brain.
This plaque, called beta-amyloid, is thought to be an important cause of the memory and behavioral symptoms of Alzheimer's.
Researchers used an experimental drug to stimulate the release of growth hormone in 208 people who had mild to moderate Alzheimer's disease. Another 208 patients were given placebo pills during the year-long study.
They successfully managed to increase the level of growth hormone in the blood of those patients receiving the drug which then stimulated the release of the insulin-like growth factor-1 hormone.
However, the drug did not manage to slow the symptoms of the disease, the study published in the journal Neurology found.
"This work suggests that targeting this hormone system may not be an effective approach to slowing the rate of Alzheimer's disease progression," said study author J.J. Sevigny of Merck Research Laboratories in Pennsylvania.
"Importantly, it challenges the common theory that hormones may attack beta-amyloid plaque in the brain and builds on the body of clinical evidence for Alzheimer's disease as we seek to develop more effective treatments."