Chapter 41: Disorders of Endocrine Growth & Metabolism

Disorders of Endocrine Growth & Metabolism explores the pathophysiology of disorders related to endocrine control of growth and energy metabolism, beginning with foundational concepts of altered endocrine function, including hypofunction, hyperfunction, and hormone resistance, which are categorized as primary, secondary, or tertiary based on their origin within the hypothalamic–pituitary–target gland axis. Pituitary dysfunction is examined through hypopituitarism, noting the typical sequence of hormone loss (GH first, ACTH last), and disorders of growth hormone (GH), where deficiency in children results in short stature and adult deficiency requires replacement therapy. Conversely, GH excess causes pituitary gigantism in youth or acromegaly in adults, characterized by pronounced soft tissue and skeletal overgrowth, coupled with significant insulin resistance and increased diabetes risk. The chapter details thyroid pathologies, explaining how TSH controls T3 and T4 actions on metabolic rate and development; hypofunction leads to acquired myxedema or congenital cretinism (intellectual disability), while hyperfunction, commonly seen in Graves disease, can escalate into life-threatening thyroid storm. Adrenal cortical function disorders involve the glucocorticoids (cortisol) and mineralocorticoids (aldosterone), covering congenital adrenal hyperplasia (CAH), which often results in ambiguous genitalia and salt-wasting, as well as adrenal insufficiency (Addison disease), marked by deficiency in all cortical hormones and hyperpigmentation. In contrast, glucocorticoid excess manifests as Cushing syndrome, causing fat redistribution and hypertension. The final major section covers Diabetes Mellitus (DM), a collection of hyperglycemic disorders, contrasting Type 1 DM (absolute insulin deficiency due to beta-cell destruction) with Type 2 DM (insulin resistance strongly linked to the metabolic syndrome, obesity, and systemic inflammation). Acute DM complications (Diabetic Ketoacidosis, Hyperosmolar Hyperglycemic State, and hypoglycemia) and chronic complications, including microvascular (neuropathy, retinopathy, nephropathy) and macrovascular disease, are thoroughly reviewed, highlighting the critical importance of tight glycemic control.