The hypothalamus is responsible for the synthesis and release of hormones that regulate the pituitary gland. Stimulation or inhibition of the pituitary hormones elicits a specific cascade of responses in peripheral target glands. In response, these glands secrete hormones that exert a negative feedback on other hormones in the hypothalam-ic-pituitary axis (Fig. 46-1). This negative feedback serves to maintain body system homeostasis. High circulating hormone levels inhibit the release of hypothalamic and anterior pituitary hormones.
Damage and destruction of the pituitary gland may result in secondary hypo-thyroidism, hypogonadism, adrenal insufficiency, growth hormone (GH) deficiency, hypopro-lactinemia, or insufficiency or absence of all anterior pituitary hormones (i.e., panhypopituitarism). A tumor (adenoma) located in the pituitary gland may result in excess secretion of a hormone or may physically compress the gland and suppress adequate hormone release. The type, location, and size of a pituitary tumor often determine a patient's clinical presentation. This chapter discusses the pathophysiology and role of pharmacotherapy in the treatment of acromegaly, GH deficiency, and hyperprolactinemia. The following hormones are discussed elsewhere in this textbook: adrenocorticotropic hormone (ACTH or corticotropin), thyroid-stimu lating hormone (TSH or thyrotropin), luteinizing hormone (LH), follicle-stimulating hormone (FSH), vasopressin (antidiuretic hormone), and oxytocin.
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