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Chapter 37: Hypothalamic & Pituitary Hormones

INTRODUCTION

The hormones produced by the hypothalamus and pituitary gland are key regulators of metabolism, growth, and reproduction. Preparations of these hormones, including recombinant forms and drugs that mimic or block their effects, are used in the treatment of a variety of endocrine disorders, including infertility.

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High-Yield Terms to Learn
Acromegaly A rare syndrome of growth hormone (GH) excess in adults characterized by abnormal growth of tissues (particularly connective tissue), metabolic abnormalities, and cardiac dysfunction
Central diabetes insipidus Also known as pituitary diabetes insipidus. A syndrome of polyuria, polydipsia, and hypernatremia caused by inadequate production of vasopressin
Gigantism A syndrome of GH excess in children and adolescents with open long bone epiphyses that results in excessive height
Gonadotropins The 2 anterior pituitary hormones (luteinizing hormone [LH] and follicle-stimulating hormone [FSH]) that regulate reproduction in males and females
Insulin-like growth factor-1 (IGF-1) A growth factor that is the primary mediator of GH effects
Prolactinoma Pituitary tumor that secretes excessive amounts of prolactin and is associated with a syndrome of infertility and galactorrhea
Tocolytic Drug used to inhibit preterm labor (magnesium sulfate; nifedipine; β2 agonists)

ANTERIOR PITUITARY HORMONES & THEIR HYPOTHALAMIC REGULATORS

The hypothalamic and pituitary hormones and their antagonists are often grouped according to the anatomic site of release of the hormone that they mimic or block—the hypothalamus for gonadotropin-releasing hormone (GnRH); the anterior pituitary for growth hormone (GH), the two gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and prolactin; or the posterior pituitary for oxytocin and vasopressin (antidiuretic hormone [ADH]). This chapter focuses on the agents used commonly; refer to the full text (Basic and Clinical Pharmacology) for hormones that are either not used clinically or are used solely for specialized diagnostic testing (thyrotropin-releasing hormone [TRH], thyroid-stimulating hormone [TSH], corticotropin-releasing hormone [CRH], adrenocorticotropic hormone [ACTH], and growth hormone-releasing hormone [GHRH]). Hormones of the anterior pituitary are central links in the hypothalamic-pituitary endocrine system (or axis; Figure 37–1). All the anterior pituitary hormones are under the control of a hypothalamic hormone, and with the exception of prolactin, all mediate their ultimate effects by regulating the production by peripheral tissues of other hormones (Table 37–1). Four anterior pituitary hormones (TSH, LH, FSH, and ACTH) and their hypothalamic regulators are subject to feedback regulation by the hormones whose production they control. The complex systems that regulate hormones of the anterior pituitary provide multiple avenues of pharmacologic intervention.

FIGURE 37–1

The hypothalamic-pituitary endocrine system. Except for prolactin, hormones released from the anterior pituitary stimulate the production of hormones by a peripheral endocrine gland, the liver, or other tissues. Prolactin and the hormones released from the posterior pituitary (vasopressin and oxytocin) act directly on target tissues. Hypothalamic factors regulate the release of anterior pituitary hormones. ACTH, adrenocorticotropin; ADH, antidiuretic hormone [vasopressin]; CRH, corticotropin-releasing hormone; DA, dopamine; FSH, follicle-stimulating hormone; GH, ...

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