522
P A R T 6
Drugs acting on the endocrine system
A
s described in Chapter 34, the endocrine system’s main
function is to maintain homeostasis. This is achieved
through a complex balance of glandular activities
that either stimulate or suppress hormone release. Too
much or too little glandular activity disrupts the body’s
homeostasis, leading to various disorders and inter
fering with the normal functioning of other endocrine
glands. The drugs presented in this chapter are those
used to either replace or interact with the hormones or
factors produced by the hypothalamus and pituitary. See
Figure 35.1 for sites of action of hypothalamic and pitui
tary agents. Box 35.1 discusses the use of these drugs in
various age groups.
DRUGS AFFECTING HYPOTHALAMIC
HORMONES
The hypothalamus uses a number of hormones or factors
to either stimulate or inhibit the release of hormones
from the anterior pituitary. Factors that stimulate the
release of hormones are growth hormone–releasing
hormone (GHRH), thyrotropin-releasing hormone
(TRH), gonadotropin-releasing hormone (GnRH),
corticotropin-releasing hormone (CRH) and prolactin-
releasing hormone (PRH). Factors that inhibit the
release of hormones are somatostatin (growth hormone–
inhibiting factor) and prolactin-inhibiting factor (PIF).
Internal
stimuli
Hypothalamus
External
stimuli
CRH, goserelin,abarelix, ganirelix,
gonadorelin, leuprorelin and
nafarelin work here
Kidney
Uterus
FSH-LH
ADH
ACTH
TSH
Prolactin
Bone
GH
Oxytocin
Posterior
pituitary
Anterior
pituitary
Oxytocin
works here
Chorionic
gonadotropin
works here
Desmopressin
works here
Octreotide,
bromocriptine,
pegvisomant
work here
Releasing and inhibiting
factors GHRH, somatostatin,
CRH, TRH, GnRH, PRH, PIF
Blood levels of hormones
regulate hypothalamus and
anterior pituitary
Somatropin
works here
Corticotropin
works here
Corpus
luteum
Ovary
Testes
Testosterone
Adrenocorticoid
hormone
Thyroid
hormone
Thyrotropin
works here
Progesterone
Oestrogen
Adrenal
Thryoid
Breast
Breast
FIGURE 35.1
Sites of action of hypothalamic/pituitary agents.
