McKenna's Pharmacology for Nursing, 2e

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P A R T 6  Drugs acting on the endocrine system

calcitonin, in direct response to serum calcium levels. Many different prostaglandins are released throughout the body in response to local stimuli in the tissues that produce them. Activation of the sympathetic nervous system directly causes release of ACTH and the adreno­ corticoid hormones to prepare the body for fight or flight. Aldosterone, an adrenocorticoid hormone, is released in response to ACTH but is also released directly in response to high potassium levels. As more is learned about the interactions of the nervous and endocrine systems, new ideas are being formed about how the body controls its intricate homeo­ stasis. When administering any drug that affects the endocrine or nervous systems, it is important for the nurse and midwife to remember how closely related all of these activities are. Expected or unexpected adverse effects involving areas of the endocrine and nervous systems often occur. ■■ The hypothalamus and pituitary operate by a series of negative feedback mechanisms called the hypothalamic–pituitary axis (HPA). The hypothalamus secretes releasing factors to cause the anterior pituitary to release stimulating hormones, which act with specific endocrine glands to cause the release of hormones. ■■ Growth hormone and prolactin are released by the anterior pituitary and directly influence cell activity. These hormones are regulated by the release of the hypothalamic inhibiting factors somatostatin and PIF in response to the levels of the pituitary hormones growth hormone and prolactin. ■■ Some hormones are not influenced by the HPA and are released in response to direct local stimulation. ■■ The endocrine system is a regulatory system that communicates through the use of hormones. ■■ Because the endocrine and nervous systems are tightly intertwined in the regulation of body homeostasis, they are often referred to as the neuroendocrine system. ■■ A hormone is a chemical that is produced within the body, is needed in only small amounts, travels to specific receptor sites to cause an increase or decrease in cellular activity and is broken down immediately. ■■ 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 pituitary is made up of three lobes: anterior, posterior and intermediate. The anterior lobe KEY POINTS CHAPTER SUMMARY

produces stimulating hormones in response to hypothalamic stimulation. The posterior lobe stores two hormones produced by the hypothalamus— ADH and oxytocin. The intermediate lobe produces endorphins and encephalins to modulate pain perception. ■■ The hypothalamus and pituitary operate by a series of negative feedback mechanisms called the hypothalamic–pituitary axis (HPA). The hypothalamus secretes releasing factors to cause the anterior pituitary to release stimulating hormones, which act with specific endocrine glands to cause the release of hormones or, in the case of growth hormone and prolactin, to stimulate cells directly. This stimulation shuts down the production of releasing factors, which leads to decreased stimulating factors and, subsequently, decreased hormone release. ■■ Growth hormone and prolactin are released by the anterior pituitary and directly influence cell activity. These hormones are regulated by the release of hypothalamic inhibiting factors in response to hormone levels or a cellular mediator. ■■ Some hormones are not influenced by the HPA and are released in response to direct local stimulation. ■■ When any drug that affects either the endocrine or the nervous system is given, adverse effects may occur throughout both systems because they are closely interrelated.

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ONLINE RESOURCES

An extensive range of additional resources to enhance teaching and learning and to facilitate understanding of this chapter may be found online at the text’s accompanying website, located on thePoint at http://thepoint.lww.com. These include Watch and Learn videos, Concepts in Action animations, journal articles, review questions, case studies, discussion topics and quizzes.

WEB LINKS

Students may want to explore up-to-date information from the following Internet sources: www.innerbody.com/image/endoov.html Travel through the virtual endocrine system. www.vivo.colostate.edu/hbooks/pathphys/endocrine Interactive review of the endocrine system and hormones.