A new study has reported that individuals with a genetic mutation that results in human growth hormone and insulin-like growth factor-1 (IGF-1) deficiencies have extremely low risk of cancer and diabetes. Mutations in growth signaling pathways have been shown to extend life span and protect against age-dependent DNA damage in yeast, as well as reducing insulin resistance and cancer in mice. To conduct the study, the authors monitored a group of Ecuadorian individuals with Laron syndrome, a rare type of dwarfism, for 22 years.
People with Laron syndrome carry mutations in the growth hormone receptor gene that prevents them from responding to human growth hormone and IGF-1, leading to severe growth hormone receptor and IGF-1 deficiencies. The study team followed 99 such individuals and 1,600 relatives of normal stature in a remote community on the slopes of the Andes. The information obtained by monitoring was combined with data from surveys to identify the cause and age of death for individuals in the community who died before the monitoring period.
Only one case of cancer (which was not lethal) and no cases of diabetes were found among the individuals with Laron syndrome. On the other hand, 17% of their non-mutation carrier relatives developed cancer and 5% developed diabetes. A possible explanation for the very low incidence of cancer was suggested by in laboratory studies: Serum from Laronís subjects protected DNA against oxidative damage and mutations, as well as promoted the suicide of cells that became highly damaged in one experiment. Serum from growth hormone receptor-deficient individuals also caused other changes that promote cellular protection and extend life-span in the laboratory. The authors also found low insulin levels and low insulin resistance in individuals with growth hormone receptor deficiency, indicating higher insulin sensitivity and possibly explaining the absence of diabetes.