Neoplasms much?
"Cancer Risk: Growth hormone causes the liver to increase its production of insulin-like growth factor (IGF-1), which is thought to play a role in breast cell growth and lactation. Elevations of blood levels of IGF-1 are associated with a greater risk for prostate and breast cancer.17,18 In laboratory tests, IGF-1 encourages breast cancer cells to multiply and is more potent in this regard even than estrogens.19,20 Slight elevations of growth hormone, with corresponding increases in IGF-1, may be one reason why tall women have a higher risk of breast cancer, compared to shorter women.21,23 One study showed that women over 5’6” have double the risk of women below 5’3”, particularly for premenopausal breast cancer.21
Several cases of leukemia have been reported in hormone-deficient children receiving hGH, but there is little evidence implicating hGH as a cause. Hormone deficiencies can be caused by brain tumors, which are sometimes treated with radiation. The leukemia may be linked to the radiation or to underlying genetic abnormalities, rather than to the hGH.
In approving hGH for use in non-hormone-deficient children, the Food and Drug Administration cited a “16-year safety history.”10 However, increased risk of hormone-related cancers may not be detected until after a longer latency period.
Renal Effects: For children who have kidney problems, growth hormone may aggravate their already poor kidney function, possibly by increasing the rate of blood flow through the kidney and the rate at which the kidneys filter the blood. One case report describes a child with preexisting kidney disease went into end-stage kidney failure after treatment with hGH.24
Metabolic Changes: Growth hormone increases the metabolism, that is, the rate at which the cells of the body consume fuel and nutrients. Some children may become unusually lean, losing body fat and becoming inappropriately muscular.25
Antibody Production: In some children, hGH stimulates the production of antibodies to growth hormone. It is presumed that these antibodies will not interfere with their own growth hormone,26 but researchers are monitoring this possibility."