Two previous, shorter studies using growth hormone insulin-like growth factor-1, or IGF-1, to treat ALS had conflicting results. A North American study found that the drug was beneficial, while a European study found no benefit.
The current two-year study found that IGF-1 does not slow the progression of weakness in the disease. ALS, also called Lou Gehrig's disease, is a progressive, fatal neurodegenerative disease that causes muscles to weaken and eventually deteriorate.
"It's disappointing that we were not able to confirm the benefit that was found in the North American study," said study author Eric J. Sorenson, MD, of the Mayo Clinic in Rochester, MN, and a member of the American Academy of Neurology. "The current treatment options for ALS are inadequate, and more effective treatments are vitally needed."
The study involved 330 people with ALS from 20 medical centers. Half were given injections of the growth hormone twice a day and half were given injections of a placebo. Researchers tested the participants' muscle strength at the beginning of the study and again five times during the study period. Researchers also tracked how long participants went without needing a tracheostomy, or a tube inserted in the neck for help with breathing, and their scores in a test of how well they can perform daily activities.
There was no difference in muscle strength between those taking the growth hormone and those taking the placebo. There were also no differences in how long the two groups went without needing a tracheostomy or in their results on the daily activities test.