Chapter 35: Hypothalamic & Pituitary Agents

Pharmacological analogues of these factors are used primarily for diagnosis, antineoplastic activity, or fertility adjuncts, including agonists like leuprolide and antagonists such as cetrorelix. Leuprolide, a prototype GnRH agonist, initially increases and then profoundly decreases luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels, and is used to treat advanced prostatic cancer and endometriosis. Next, agents affecting the anterior pituitary are examined, most notably those acting as or against growth hormone (GH). GH deficiency leads to dwarfism in children or somatotropin deficiency syndrome (SDS) in adults. The prototype GH agonist, somatropin, is a genetically engineered hormone used for replacement therapy. Conversely, GH hypersecretion results in gigantism if it occurs before the epiphyseal plates close, or acromegaly (thickening of bony surfaces) if it occurs after puberty. Treatment for GH excess involves GH antagonists, such as the somatostatin analogues octreotide and lanreotide, or the prototype bromocriptine mesylate, a dopamine agonist that inhibits GH secretion in certain patients. The chapter also addresses drugs affecting the posterior pituitary, which stores antidiuretic hormone (ADH or vasopressin) and oxytocin. A lack of ADH results in diabetes insipidus, characterized by the production of copious amounts of glucose-free urine, requiring replacement therapy with the ADH analogue desmopressin (the prototype). Conversely, Syndrome of Inappropriate Antidiuretic Hormone (SIADH), caused by excessive ADH, is treated with vasopressin blockers like conivaptan and tolvaptan to increase water excretion and restore serum sodium balance. Nursing care considerations across all classes emphasize continuous monitoring of endocrine function, particularly blood glucose and electrolyte levels, evaluation of growth and development (in children), appropriate teaching regarding injection site rotation, and crucial oversight of administration techniques for nasal forms, especially for desmopressin, to prevent water intoxication or local complications.