526
P A R T 6
Drugs acting on the endocrine system
deficiency before any other signs and symptoms occur.
Hypopituitarism may occur as a result of developmen
tal abnormalities or congenital defects of the pituitary,
circulatory disturbances (e.g. haemorrhage, infarction),
acute or chronic inflammation of the pituitary and
pituitary tumours. GH deficiency in children results
in short stature (
dwarfism
). Adults with somatropin
deficiency syndrome (SDS) may have hypopituitarism
as a result of pituitary tumours or trauma, or they
may have been treated for GH deficiency as children,
resulting in a shutdown of the pituitary production of
somatotropin.
GH deficiency was once treated with GH injections
extracted from the pituitary glands of cadavers. The
supply of GH was therefore rather limited and costly
(Box 35.2). Synthetic human GH is now available from
recombinant DNA sources, using genetic engineering.
Synthetic GH is expensive, but it is thought to be safer
than cadaver GH and is being used increasingly to treat
GH deficiencies. Somatropin (
Genotropin
,
Omnitrope
,
Saizen
and others) and somatropin recombinant DNA
(rDNA) origin (
Zomacton
) are used for GH replacement
today.
Therapeutic actions and indications
In clinical practice, the agents that are used purely as a
replacement for anterior pituitary hormones are those
acting as GH—somatropin and somatropin rDNA
origin. Both of these drugs are produced with the use
of recombinant DNA technology. See Table 35.2 for
indications.
In the past, growth hormone (GH) therapy was
expensive and unsafe. The use of cadaver pituitaries
resulted in unreliable hormone levels and, in many cases,
hypersensitivity reactions to the proteins found in the
drug. With the advent of genetic engineering and the
development of safer, more reliable forms of growth
hormone, there has been a surge in the use of the drug
to treat children with short stature. Even so, the drug is
still costly and not without adverse effects.
Growth hormone can be used to treat growth failure
caused either by lack of growth hormone or by renal
failure. It also can help children with normal growth
hormone levels who are just genetically small. Before
the drug is prescribed, the child must undergo screening
procedures and specific testing (including radiographs
and blood tests) and must display a willingness to
have regular injections. The child taking this drug will
need to have pretherapy and periodic tests of thyroid
function, blood glucose levels, glucose tolerance tests,
and tests for growth hormone antibodies (a risk that
increases with the length of therapy). In addition,
radiographs of the long bones will be taken to monitor
for closure of the epiphyses, a sign that the drug must
be stopped. Because the child who is taking growth
hormone may experience sudden growth, they will
need to be monitored for nutritional needs, as well as
psychological trauma that may occur with the sudden
change in body image. Insulin therapy and replacement
thyroid therapy may be needed, depending on the child’s
response to the drug. (See also Focus on safe medication
administration related to growth hormone therapy.)
■■
BOX 35.2
Growth hormone therapy
TABLE 35.2
DRUGS IN FOCUS Drug affecting anterior pituitary hormones (continued)
Drug name
Dosage/route
Usual indications
Drugs affecting other anterior pituitary hormones
cabergoline (Bergoline)
2–3 mg PO daily
Treatment of signs and symptoms of
Parkinson’s disease
chorionic gonadotropin
(Pregnyl)
Dose varies with indication; 4000–10,000
International Units IM one to three times per
week is not unusual
Treatment of male hypogonadism,
to induce ovulation in females with
functioning ovaries, for treatment of
prepubertal cryptorchidism when there
is no anatomical obstruction to testicular
movement
choriogonadotropin alfa
(Ovidrel)
250 mcg SC given 1 day after last dose of a
follicle-stimulating hormone (FSH) stimulator
Induction of ovulation in infertile females
who have been pretreated with FSH
quinagolide (Norprolac)
25 mcg/day PO for 3 days, then 50 mcg/day
for further 3 days then 75–125 mcg/day PO
Treatment of hyperprolactinaemia
thyrotropin alfa (Thyrogen)
0.9 mg IM, followed by 0.9 mg IM in 24 hours
Adjunctive treatment for post-radioiodine
ablation of thyroid tissue in people with
near-total thyroidectomy and well-
differentiated thyroid cancer without
metastasis
