Introduction:
Human growth hormone (hGH) is a naturally occurring polypeptide
hormone secreted by the pituitary gland and is essential for
body growth. Daily secretion of hGH increases throughout
childhood, peaking during adolescence, and steadily declining
thereafter. In 1985, synthetic hGH was developed and
approved by the FDA for specific uses. However, it is
commonly abused by athletes, bodybuilders, and aging adults for
its ability increase muscle mass and decrease body fat, as well
as its purported potential to improve athletic performance and
reverse the effects of aging.
Licit Uses:
Several FDA-approved injectable hGH preparations are available
by prescription from a supervising physician for clearly and
narrowly defined indications. In children, hGH is approved
for the treatment of poor growth due to Turner’s syndrome,
Prader-Willi syndrome, and chronic renal insufficiency, hGH
insufficiency/deficiency, for children born small for
gestational age, and for idiopathic short stature.
Accepted medical uses in adults include the treatment of the
wasting syndrome of AIDS and hGH deficiency. The
recommended dosage is 40 mg/kg/day for children and 25 mg/kg/day
for adults. The FDA-approved injectable formulations are
available as liquid preparations, or as powder with a diluent
for reconstitution.
Chemistry and Pharmacology:
Using recombinant DNA technology, two forms of synthetic hGH
were developed, somatropin and somatrem. Somatropin is
identical to the endogenous pituitary-derived hGH, whereas
somatrem has an extra amino acid on the N-terminus. Both
synthetic forms have similar biological actions and potencies as
the endogenous hGH polypeptide. Synthetic hGH also is chemically
indistinguishable from the naturally occurring hormone in blood
and urine tests.
hGH binds to growth hormone receptors present on cells
throughout the body. hGH functions to regulate body
composition, fluid homeostasis, glucose and lipid metabolism,
skeletal muscle and bone growth, and possibly cardiac
functioning. Sleep, exercise, and stress all increase the
secretion of hGH.
The use of hGH is associated with several adverse effects
including edema, carpal tunnel syndrome, joint pain, muscle
pain, and abnormal skin sensations (e.g., numbness and
tingling). It may also increase the growth of pre-existing
malignant cells, and increase the possibility of developing
diabetes.
hGH is administered by subcutaneous or intramuscular injection.
The circulating half-life of hGH is relatively short half-life
(20-30 minutes), while its biological half-life is much longer
(9-17 hours) due to its indirect effects.
Illicit Uses:
Human growth hormone is illicitly used as an anti-aging agent,
to improve athletic performance, and for bodybuilding purposes.
It is marketed, distributed, and illegally prescribed off-label
to aging adults to replenish declining hGH levels and reverse
age-related bodily deterioration. It is also abused for
its ability to alter body composition by reducing body fat and
increasing skeletal muscle mass. It is often used in
combination with other performance enhancing drugs, such as
anabolic steroids. Athletes also use it to improve their
athletic performance, although the ability of hGH to increase
athletic performance is debatable.
Abuser Population:
Athletes, bodybuilders, and aging adults are the primary abusers
of hGH. Because the illicit use of synthetic hGH is
difficult to detect, its use in sports is believed to be
widespread. Over the past few years, numerous professional
athletes have admitted to using hGH. Bodybuilders, as well
as celebrities also purportedly use it for its ability to alter
body composition. Aging adults looking to reverse the
effects of aging are increasingly using synthetic hGH.
Illicit Distribution:
The illicit distribution of hGH occurs as the result of
physicians illegally prescribing it for off-label uses, and for
the treatment of FDA-approved medical conditions without
examination and supervision. Illicit distribution also
involves diverted hGH obtained through theft, smuggled hGH
illegally imported from other countries, and counterfeit hGH.
The illicit distribution of injectable synthetic hGH
formulations is thought to be primarily through Internet
pharmacies, as well as wellness and anti-aging clinics and
websites. Internet pharmacies are often partnered with a
physician willing to write prescriptions for a fee without a
physical examination. Individuals may also obtain hGH
without a prescription through the black market. hGH is
often marketed with other performance enhancing drugs (e.g.,
anabolic steroids).
According to the National Forensic Laboratory Information System
(NFLIS), law enforcement officials submitted 27 hGH
items/exhibits to state and local forensic laboratories between
2004 and 2008. NFLIS data indicate that the number of
seized hGH items have increased recently. In 2006, 3 items
were submitted to state and local laboratories. In 2007, 7
items were submitted. Ten items were submitted in 2008.
Various oral preparations (e.g., sprays and pills) purported to
contain hGH are also marketed and distributed. However,
hGH is only available in the injectable form. The hGH
molecule is too large for absorption across the lining of the
oral mucosa and the hormone is digested by the stomach before
absorption can occur.
Control Status:
Human growth hormone is not controlled under the Controlled
Substances Act (CSA). However, as part of the 1990
Anabolic Steroids Control Act, the distribution and possession,
with the intent to distribute, of hGH “for any use…other
than the treatment of a disease or other recognized medical
condition, where such use has been authorized by the Secretary
of Health and Human Services…and pursuant to the order of a
physician…” was criminalized as a five-year felony under the
penalties chapter of the Food, Drug, and Cosmetics Act of the
FDA.
hGH is listed by the World Anti-Doping Agency and the
International Olympic Committee as a performance enhancing drug
barring athletes from using it.
Comments and additional information are welcomed by the
Office of Diversion Control, Drug and Chemical Evaluation
Section.
Fax 202-307-1263, telephone 202-307-7183, or Email ODE@usdoj.gov.