McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 3 4 Introduction to the endocrine system

Internal stimuli

External stimuli

Hypothalamus

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

Kidney

ADH

GH

Posterior pituitary

Bone

Breast

Anterior pituitary

Oxytocin

Prolactin

Breast

Uterus

FSH-LH

TSH

ACTH

Thryoid

Thyrotropin works here

Adrenal

Ovary

Testes

Corpus luteum

Thyroid hormone

Adrenocorticoid hormone

Testosterone

Progesterone Oestrogen

Blood levels of hormones regulate hypothalamus and anterior pituitary

FIGURE 34.1  The traditional endocrine system. The hypothalamus secretes releasing factors to stimulate the parathyroid gland to produce stimulating factors that enter the circulation and react with specific target glands, which produce endocrine hormones.

to be stored in the posterior pituitary until the hypothalamus stimulates their release.

KEY POINTS

■■ As the “master gland” of the neuroendocrine system, the hypothalamus helps to regulate the central and autonomic nervous systems and the endocrine system to maintain homeostasis. ■■ The hypothalamus produces stimulating and inhibiting factors that travel to the anterior pituitary to stimulate the release of pituitary hormones or block the production of certain pituitary hormones when levels of target hormones get too high. ■■ The hypothalamus is connected to the posterior pituitary by a nerve network that delivers the hypothalamic hormones ADH and oxytocin

THE PITUITARY GLAND The pituitary gland is located in the skull in the bony sella turcica under a layer of dura mater. It is divided into three lobes: an anterior lobe, a posterior lobe and an intermediate lobe. Traditionally, the anterior pituitary was known as the body’s master gland because it has so many important functions and, through feedback mech­ anisms, regulates the function of many other endocrine glands. In addition, its unique and protected position in