A controversial but approved use of GH is for children with idiopathic short stature (ISS). This is a heterogeneous population that has in common no identifiable cause of the short stature. Some have arbitrarily defined ISS clinically as having a height at least 2.25 standard deviations below normal for children of the same age and a predicted adult height that is less than 2.25 standard deviations below normal. In this group of children, many years of GH therapy result in an average increase in adult height of 4–7 cm (1.57–2.76 inches) at a cost of $5000–$40,000 per year. The complex issues involved in the cost-risk-benefit relationship of this use of GH are important because an estimated 400,000 children in the United States fit the diagnostic criteria for ISS.
Treatment of children with short stature should be carried out by specialists experienced in GH administration. Dose requirements vary with the condition being treated, with GH-deficient children typically being most responsive. Children must be observed closely for slowing of growth velocity, which could indicate a need to increase the dosage or the possibility of epiphyseal plate fusion or intercurrent problems such as hypothyroidism or malnutrition.
Other Uses of Growth Hormone
Growth hormone affects many organ systems and also has a net anabolic effect. It has been tested in a number of conditions that are associated with a severe catabolic state and is approved for the treatment of wasting in patients with AIDS. In 2004, GH was approved for treatment of patients with short bowel syndrome who are dependent on total parenteral nutrition (TPN). After intestinal resection or bypass, the remaining functional intestine in many patients undergoes extensive adaptation that allows it to adequately absorb nutrients. However, other patients fail to adequately adapt and develop a malabsorption syndrome. Growth hormone has been shown to increase intestinal growth and improve its function in experimental animals. Benefits of GH treatment for patients with short bowel syndrome and dependence on TPN have mostly been short-lived in the clinical studies that have been published to date. Growth hormone is administered with glutamine, which also has trophic effects on the intestinal mucosa.
Growth hormone is a popular component of “anti-aging” programs. Serum levels of GH normally decline with aging; anti-aging programs claim that injection of GH or administration of drugs purported to increase GH release are effective anti-aging remedies. These claims are largely unsubstantiated. In contrast, studies in mice and the nematode Caenorhabditis elegans have clearly demonstrated that analogs of human GH and IGF-I consistently shorten life span and that loss-of-function mutations in the signaling pathways for the GH and IGF-I analogs lengthen life span. Another use of GH is by athletes for a purported increase in muscle mass and athletic performance. Growth hormone is one of the drugs banned by the International Olympic Committee.
In 1993, the FDA approved the use of recombinant bovine growth hormone (rbGH) in dairy cattle to increase milk production. Although milk and meat from rbGH-treated cows appear to be safe, these cows have a higher incidence of mastitis, which could increase antibiotic use and result in greater antibiotic residues in milk and meat.