Common side effects of short-term human growth hormone supplementation in children include excessive leanness, joint pain, and increased blood glucose levels, according to the Physician's Committee for Responsible Medicine. Long-term supplementation with human growth hormone results in an increased risk of colorectal cancer and Hodgkin's disease.
Human growth hormone is commonly used to treat children with predicted adult heights less than 5 feet 3 inches for males or 4 feet 11 inches for females, reports the Physician's Committee for Responsible Medicine. Treated children do not seem to be at an increased risk for leukemia, which is the most common form of cancer in children. The long-term effects of this treatment are not entirely understood as of 2015, however. Human growth hormone significantly increases the amount of insulin-like growth factor in a person's blood. This hormone is linked to increased rates of breast and prostate cancer, as it causes rapid cell multiplication.
A 2002 study by British researchers linked long-term human growth hormone supplementation with higher risks of cancer, cautions the Physician's Committee for Responsible Medicine. The individuals studied had undergone human growth hormone supplementation and were monitored from 1985 to 2000. These individuals were relatively young, and few were over 45 to 50 years of age, but they had higher-than-average cancer rates for their age group. Scientists also have found that individuals with naturally high levels of human growth hormone are at an increased risk for cancer, carpal tunnel syndrome and joint issues.