Chapter 41: Disorders of Endocrine Control of Growth and Metabolism

Acromegaly results from excessive growth hormone secretion, typically due to a pituitary adenoma, and is confirmed through elevated baseline serum growth hormone concentrations that fail to suppress appropriately during glucose tolerance testing, alongside elevated insulin-like growth factor-1 levels. Clinical manifestations include progressive enlargement of facial features and extremities, cardiovascular complications such as hypertension, glucose intolerance, and joint pathology. Hypothyroidism represents insufficient thyroid hormone production, identifiable through suppressed free thyroxine levels and elevated thyroid-stimulating hormone, causing metabolic slowing with characteristic symptoms of weight gain, skin dryness, cold sensitivity, fatigue, and cognitive impairment. Adrenal insufficiency, whether primary autoimmune destruction or secondary to pituitary dysfunction, presents with biochemical evidence of reduced plasma cortisol and elevated adrenocorticotropic hormone in primary disease. Clinical presentation includes nonspecific constitutional symptoms, weight loss, distinctive hyperpigmentation from elevated adrenocorticotropic hormone stimulation, and electrolyte abnormalities including hyponatremia and hyperkalemia that precipitate orthostatic hypotension and circulatory collapse. The chapter emphasizes diagnostic criteria distinguishing primary from secondary hormone deficiencies, interpretation of hormone response to stimulation and suppression testing, and recognition of how endocrine dysfunction produces systemic metabolic consequences. Diabetes mellitus is discussed regarding glycemic monitoring through hemoglobin A1C measurement and the relationship between metabolic dysregulation and endocrine pathology. Understanding the pathophysiological mechanisms of these disorders enables clinicians to recognize subtle clinical presentations and institute appropriate hormone replacement or suppressive therapy.