What is HGH?
Janice Skelton, ND
Human growth hormone (hGH), also known as somatotrophin, is the most abundant hormone produced by the pituitary gland. Somatotrophes—the cells that make growth hormone—make up 50% of the anterior pituitary glands cells. Growth hormone (GH) stays in the bloodstream long enough for its reuptake into the liver where it is converted into growth factors, the most abundant being insulin-like growth factor (IGF-1, or somatomedin C). IGF-1 is directly responsible for most of the actions of growth hormone, such as stimulating the growth of bone, muscle, cartilage, kidneys and skin. Via negative feedback, IGF-1 inhibits further growth hormone production.1 Growth hormone secretion is stimulated by growth hormone-releasing hormone (GHRH) and inhibited by somatostatin. Other hormones that modulate growth hormone include cortisol, which inhibits growth hormone, and sex steroids and ghrelin, both of which stimulate growth hormone.2,3
Testing for HGH
Growth hormone is secreted in rhythmic pulses during the early hours of deep sleep. GH secretion is also stimulated by exercise, protein ingestion, and hypoglycemia. As a result, there is wide variation in GH secretion levels.
The following 4 laboratory tests are commonly used to diagnose GH deficiency:
- Serum IGF-1: Compared to GH, IGF-1 is less affected by time of day or recent food intake. Because IGF-1 levels typically parallel those of GH, serum IGF-1 is a more accurate indicator of GH status. The test is often used to identify patients with GH deficiency, pituitary insufficiency, and acromegaly. IGF-1 levels can be affected by nutritional status (malnutrition), liver and thyroid function, and age. Low serum IGF-1, by itself, is also not diagnostic of GH deficiency, so is sometimes ordered along with GH stimulation tests, which can help identify primary GH deficiency (due to a pituitary problem).
- Serum GH: Since levels of GH levels vary greatly due to its episodic secretion and factors such as stress, exercise, diet, hypoglycemia, medications, and nutritional supplements, a single GH measurement is unreliable.
- GH stimulation test: This test measures the ability of the pituitary gland to release GH after being stimulated to release the hormone. After a baseline blood sample is collected, provocation agents such as insulin or arginine4 are administered intravenously and GH is subsequently measured in 4 additional blood samples, collected every 30 minutes. In adults, if provocation fails to raise GH levels, then pan-hypopituitarism and/or adult GH deficiency is present. In children, this indicates GH deficiency. GH stimulation tests also help physicians to determine if additional testing is required.
- Serum IGFBP-3: (Insulin-like growth factor binding protein-3) may also be used to confirm GH deficiency, especially when IGF-1 is normal. IGF-1 in blood is bound to binding proteins, IGFBP-3 being the most abundant.5
Approved Uses of Human Growth Hormone
U.S. Food and Drug Administration (FDA)-approved injectable hGH is available by prescription for treating children with impaired growth due to Turner’s syndrome, Prader-Willi syndrome, or chronic renal insufficiency; children with growth hormone insufficiency or deficiency; children born small-for-gestational age with poor growth after 2 years of age; and children with idiopathic short stature who are more than 2.5 standard deviations below the mean.6 Accepted medical uses in adults include the treatment of the wasting syndrome of AIDS and growth hormone deficiency (usually related to pituitary tumor).7
Although controversial, off-label prescribing of drugs or devices (product) is an important component of modern medicine. Off-label use is when a product is prescribed for circumstances that have not been approved by the FDA. Once the FDA approves a product for marketing, it is at the physicians’ discretion to prescribe the product for indications or population groups, typically geriatrics or pediatrics, that are not included on the label. Drugs may be administered by methods or at dosages not specified on the label; the omission of a use on a product’s label simply means that the FDA has not yet reviewed the product for that particular use.
In general, it is the medical community which has the responsibility of determining when off-label prescribing is appropriate. Physicians must determine that there is sufficiently solid evidence to justify off-label use prior to prescribing and are justified in prescribing off-label uses of product when backed by scientific and medical evidence.8 HGH is an exception to this rule, since the FDA specifically prohibits off-label uses of hGH. Some physicians prescribe it illicitly, with the goal of replenishing declining levels of growth hormone and reversing age-related deterioration.
HGH is popular with bodybuilders, athletes and celebrities, since it decreases body fat and increases lean body mass by increasing the mass of skeletal muscle. The groups most likely to abuse hGH are those wishing to reverse the effects of aging.6
In 2009, hGH was placed on the Drug Enforcement Administration (DEA)’s list of Drugs and Chemicals of Concern, along with LSD and oxycodone. HGH is not a controlled substance under federal law; it is, however, a controlled substance in some states.
The Food Drug and Cosmetic Act (FDCA) gives the DEA the authority to investigate violations of the FDCA involving hGH. According to the FDCA, the ”distribution and possession, with the intent to distribute hGH for any use….other than the treatment of disease or recognized medical condition, where such has been authorized by the Secretary of Health and Human Services…pursuant to the order of a physician is punishable as a five-year felony.”9 It is not clear if distribution includes prescribing by a physician. The DEA clearly states: “The illicit distribution of hGH occurs as the result of physicians illegally prescribing it for off-label uses.”
Additionally, hGH is listed by the World Anti-Doping Agency and the International Olympic Committee as a performance-enhancing drug, hence barring athletes from using it.6
Unlike other hormone replacement therapy, physicians prescribing hGH replacement must strictly adhere to DEA, FDA, and state guidelines to prescribe only when medically necessary and within government-regulated requirements. HGH may not be prescribed for any other than the approved conditions.
Janice Skelton, NMD currently practices at Transform You in Tempe, Arizona as a hormone replacement and weight loss specialist. She is a 1999 graduate of NCNM and is passionate about helping people to live fuller lives. When not practicing medicine, she is an avid yoga practitioner and teacher and the owner of RINEW Yoga Fusion in Mesa, Arizona.
- Corpas E, Harman MS, Blackman MR. Human growth hormone and human ageing. Endocr Rev. 1993;14(1):20-39.
- Klatz R, Kahn C. Grow Young With HGH: The Amazing Medically Proven Plan to Reverse Aging. New York, NY: Harper Collins Publishers; 1998.
- Bowen RA. The Hypothalamus and Pituitary Gland: Introduction and Index. Fort Collins, CO: Colorado State University. Updated March 20, 2003. www.vivo.colostate.edu/hbooks/pathphys/endocrine/hypopit/. Accessed May 30, 2013.
- Pagano KD, Pagano TJ. Mosby’s Manual of Diagnostic Laboratory Tests. 3rd ed. St. Louis, MO: Mosby, Inc; 2006.
- IGF-1. Lab Tests Online. Updated July 11, 2011. http://labtestsonline.org/understanding/analytes/igf1/tab/test. Accessed June 1, 2013.
- Human Growth Hormone. Drug Enforcement Administration; Office of Diversion Control; Drug & Chemical Evaluation Section. August 2011. http://www.deadiversion.usdoj.gov/drug_chem_info/hgh.pdf. Accessed May 30, 2013.
- Hintz RL. Growth hormone: uses and abuses. BMJ. 2004;328(7445):907-908.
- Dresser R, Frader J. Off-label prescribing: a call for heightened professional and governmental oversight. J Law Med Ethics. 2009;37(3):476-486.
- Stilling WJ. January 2010. DEA Places Use of Human Growth Hormone on List of Drugs and Chemicals of Concern. E-Journal of Age Management Medicine. January, 2010. http://archive.agemed.org/default.asp?page=LegalBriefsJan2010. Accessed May 30, 2013.