November 24 (HealthDay News) -- The growth hormone known as insulin-like growth factor-1 (IGF-1) showed no benefit for people with amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease.

The two-year U.S. study included 330 patients from 20 medical centers.

Two previous, shorter studies had produced conflicting results. One North American study found that IGF-1 was beneficial, while a European study found no benefit for people with ALS, a progressive, fatal neurodegenerative disease that causes muscles to weaken and deteriorate.

This new study concluded that IGF-1 does not slow progression of muscle weakness.

"It's disappointing that we were not able to confirm the benefit that was found in the North American study. The current treatment options for ALS are inadequate, and more effective treatments are vitally needed," study author Dr. Eric J. Sorenson, of the Mayo Clinic in Rochester, Minn., said in an American Academy of Neurology news release.

Half the patients in the new study were given injections of IGF-1 while the other half received a placebo. The patients' muscle strength was tested at the start of the study and again five times during the two-year study period. Sorenson and his colleagues also tracked how long patients went without needing a tracheostomy (a tube inserted in the neck to assist breathing) and their scores on ongoing tests of their ability to perform daily activities.

The study found no differences between the two groups in muscle strength, how long they went without needing a tracheostomy, or in their ability to perform daily activities.

The findings were published in the Nov. 25 issue of the journal Neurology.

SOURCE: American Academy of Neurology, news release, Nov. 24, 2008