Chapter 20: Alterations of Hormonal Regulation

Hormonal alterations arise through multiple mechanisms including hypersecretion and hyposecretion, abnormal feedback regulation, ectopic hormone production from non-endocrine tissues, defective carrier proteins, and receptor dysfunction from downregulation or genetic mutations. The hypothalamic-pituitary axis serves as the central regulatory hub, and dysfunction here produces syndromes of inappropriate antidiuretic hormone secretion characterized by water retention and hyponatremia, versus diabetes insipidus causing polyuria and hypernatremia through either neurogenic, nephrogenic, or primary polydipsia pathways. Pituitary insufficiency results from infarction, neoplastic growth, trauma, or infection, eliminating secretion of adrenocorticotropic hormone, thyroid-stimulating hormone, growth hormone, and gonadotropins, while adenomatous expansion causes mass effects and hormone excess, with prolactinoma representing the most prevalent functional tumor. Thyroid pathology encompasses autoimmune hyperthyroidism from thyroid receptor antibodies producing goiter and exophthalmos, alongside hypothyroidism from autoimmune thyroiditis or iodine deficiency, with congenital disease causing irreversible neurological damage if untreated. Parathyroid disorders create opposing mineral metabolism problems through either excess parathyroid hormone causing bone resorption and kidney stone formation, or hormone deficiency producing hypocalcemia with neuromuscular hyperexcitability. Diabetes mellitus represents the most prevalent endocrine disorder, with autoimmune beta cell destruction defining type 1 disease and insulin resistance with relative insufficiency characterizing type 2 disease, both progressing toward microvascular complications in the retina and kidney and macrovascular atherosclerotic disease. Adrenal cortical excess from pituitary or ectopic adenomas produces central adiposity and metabolic dysfunction, mineralocorticoid excess causes sodium retention and hypokalemia, while adrenal insufficiency from autoimmune destruction creates electrolyte derangements and hemodynamic instability. Adrenal medullary tumors release catecholamines episodically, producing paroxysmal hypertension and sympathetic symptoms. Understanding these pathophysiological mechanisms enables clinicians to recognize disease patterns, interpret diagnostic findings, and implement appropriate therapeutic interventions across diverse endocrine dysfunction.