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P A R T 6
Drugs acting on the endocrine system
D
rugs affecting other anterior
pituitary hormones
Drugs that affect growth hormone are the most com
monly used drugs affecting anterior pituitary hormones.
There are several other anterior pituitary hormones
that can now be affected by drugs. The other anterior
pituitary hormones that are available for pharmaco
logical use include chorionic gonadotropin (
Pregnyl
),
choriogonadotropin alfa (
Ovidrel
) and thyrotropin alfa
(
Thyrogen
) (not available in New Zealand).
Chorionic gonadotropin acts like LH and stimulates
the production of testosterone and progesterone. Usual
indications are presented in Table 35.2. (See Chapters 40
and 41 for nursing implications.) Choriogonadotropin
alfa is used as a fertility drug to induce ovulation in
women treated with FSH (see Chapters 40 and 41).
Thyrotropin alfa is used as adjunctive treatment for
radioiodine ablation of thyroid tissue remnants in people
who have undergone a near-total to total thyroidectomy
for well-differentiated thyroid cancer and who do not
have evidence of metastatic thyroid cancer.
Cabergoline (
Bergoline
) acts on dopamine receptors
located on pituitary lactotrophic cells to decrease pro
lactin secretion.
■■
Hypothalamic releasing factors stimulate the
anterior pituitary to release hormones, which in
turn stimulate endocrine glands or cell metabolism.
The anterior pituitary hormones are mostly used for
diagnostic testing, for treating some cancers or in
fertility programs.
■■
In children, deficiency of GH may be responsible for
dwarfism; in adults it is associated with somatropin
deficiency syndrome.
■■
GH may be replaced by substances produced by
recombinant DNA processes, which are safer than
replacement drugs used in the past.
■■
In cases of GH excess, drugs are used to block
the effects of GH. Care must be taken to monitor
KEY POINTS
these individuals because of the systemic effects of
the drugs.
DRUGS AFFECTING POSTERIOR
PITUITARY HORMONES
The posterior pituitary stores two hormones produced
in the hypothalamus: antidiuretic hormone (ADH,
also known as vasopressin) and oxytocin. Oxytocin
stimulates milk ejection or “let down” in breastfeed
ing women. In pharmacological doses, it can be used
to initiate or improve uterine contractions in labour.
Oxytocin is discussed in Chapter 40.
ADH possesses antidiuretic, haemostatic and vaso
pressor properties. Posterior pituitary disorders can
occur secondary to metastatic cancer, lymphoma, dis
seminated intravascular coagulation (discussed in
Chapter 48) or septicaemia. Posterior pituitary dis
orders that are seen clinically involve ADH release
and include
diabetes insipidus
, which results from
insufficient secretion, and syndrome of inappropri
ate antidiuretic hormone (SIADH), which occurs with
excessive secretion of ADH. Diabetes insipidus can be
treated pharmacologically. (
See the Critical thinking
scenario related to diabetes insipidus and posterior
pituitary hormones.
)
Diabetes insipidus is characterised by the production
of a large amount of dilute urine containing no glucose.
Blood glucose levels are higher than normal, and the
body responds with polyuria (excessive urine), poly
dipsia (excessive thirst) and dehydration. With this rare
metabolic disorder, individuals produce large quantities
of dilute urine and are constantly thirsty. Diabetes insip
idus is caused by a deficiency in the amount of posterior
pituitary ADH and may result from pituitary disease or
injury (e.g. head trauma, surgery, tumour). The condi
tion can be acute and short in duration or it can be a
chronic, lifelong problem.
ADH itself is never used as therapy for diabetes
insipidus. Instead, synthetic preparations of ADH,
which are purer and have fewer adverse effects, are used.
The ADH preparations currently available are desmo
pressin (
Minirin
,
Octostim
) and vasopressin (
Pitressin
)
(see Table 35.3).
Therapeutic actions and indications
ADH is released in response to increases in plasma
osmolarity or decreases in blood volume. It produces its
antidiuretic activity in the kidneys, causing the cortical
and medullary parts of the collecting duct to become
permeable to water, thereby increasing water reabsorp
tion and decreasing urine formation. These activities
reduce plasma osmolarity and increase blood volume.
See Table 35.3 for usual indications for desmopressin
and vasopressin.
■
■
Monitor for adverse effects (hypothyroidism,
glucose intolerance, nutritional imbalance, GI
disturbances, headache, dizziness, cholecystitis).
■
■
Evaluate the effectiveness of the teaching plan
(person can name drug, dosage, adverse effects
to watch for and specific measures to avoid them;
family member can demonstrate proper technique
for preparation and administration of drug).
■
■
Monitor the effectiveness of comfort measures and
compliance with the regimen.
