The researchers used a rat model to explore the effects of growth hormone and another compound, IGF-1 (insulin-like growth factor 1) on adult rats and found paradoxical effects, according to William E. Sonntag, Ph.D., professor of physiology and pharmacology at Wake Forest University Baptist Medical Center and the lead investigator.
"Things that happen when you are an adolescent may have an impact on how long you live and what you die of," he said.
"The presence of growth hormone and IGF-1 is necessary for maintenance of cognitive function and prevention of cartilage degeneration," Sonntag and his colleagues reported in an article in Endocrinology, published on-line today. But the hormones also increase cancer and other diseases that limit lifespan.
The researchers developed a strain of dwarf rats that were naturally deficient in both growth hormone and in IGF-1. To mimic the rise in growth hormone and IGF-1 during adolescence in normal rats, some of these deficient rats were given growth hormone while they were between 4 and 14 weeks of age ?rat adolescence. Then hormone treatment was stopped and the animals had lower growth hormone and IGF-1 levels the rest of their lives.
That had an effect on cancer: 88 percent of "normal" male rats have tumors at death. The male rats that had a lifelong deficiency of growth hormone had substantially fewer tumors ?63 percent ?and the percent of tumors that were fatal was reduced from 57 percent to 31 percent.
The same pattern occurred for kidney disease, which was found in 74 percent of the normal male animals at the time of their deaths. None of the growth-hormone deficient animals developed kidne
Source:Wake Forest University Baptist Medical Center