McKenna's Pharmacology for Nursing, 2e

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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

CRH, goserelin,abarelix, ganirelix, gonadorelin, leuprorelin and nafarelin work here

External stimuli

Hypothalamus

Desmopressin works here

Releasing and inhibiting factors GHRH, somatostatin, CRH, TRH, GnRH, PRH, PIF

Somatropin works here

Kidney

ADH

Octreotide, bromocriptine, pegvisomant work here

GH

Posterior pituitary

Bone

Breast

Anterior pituitary

Oxytocin

Oxytocin works here

Prolactin

Breast

Uterus

FSH-LH

TSH

ACTH

Thryoid

Chorionic gonadotropin works here

Thyrotropin works here

Adrenal

Ovary

Testes

Corticotropin works here

Corpus luteum

Thyroid hormone

Adrenocorticoid hormone

Testosterone

Progesterone Oestrogen

Blood levels of hormones regulate hypothalamus and anterior pituitary

FIGURE 35.1  Sites of action of hypothalamic/pituitary agents.