Summary This document provides comprehensive MBChB-level revision notes on endocrine pathology, covering disorders of the pituitary, thyroid, parathyroid, adren
Summary This document provides comprehensive MBChB-level revision notes on endocrine pathology, covering disorders of the pituitary, thyroid, parathyroid, adrenal glands, and pancreas, as well as multiple endocrine neoplasia syndromes. It includes detailed explanations of anatomy, pathophysiology, clinical features, diagnosis, and treatment for a wide range of endocrine conditions. Key Points - Pituitary disorders include hyperpituitarism (e.g., adenomas causing hormone excess or mass effects) and hypopituitarism (deficiency of pituitary hormones). - Thyroid disorders encompass goiters, hypothyroidism (e.g., Hashimoto's), hyperthyroidism (e.g., Graves' disease), and various types of thyroiditis and tumors. - Parathyroid disorders involve hyperparathyroidism (primary, secondary, tertiary) leading to hypercalcemia and hypoparathyroidism causing hypocalcemia. - Adrenal disorders cover hyperfunction (Cushing syndrome, hyperaldosteronism, adrenogenital syndromes) and hypofunction (Addison's disease). - Pancreatic endocrine disorders primarily focus on diabetes mellitus (T1DM, T2DM, MODY, gestational DM) and its acute and chronic complications, as well as pancreatic tumors. - Multiple Endocrine Neoplasia (MEN) syndromes are inherited disorders characterized by tumors in multiple endocrine glands, with MEN1, MEN2A, and MEN2B being key examples. Detailed Notes TOPIC 1: PITUITARY DISORDERS Anatomy & Overview The pituitary gland (hypophysis) is located in the sella turcica and has two main lobes: the anterior pituitary (adenohypophysis) , responsible for producing GH, TSH, ACTH, FSH, LH, and Prolactin, and the posterior pituitary (neurohypophysis) , which stores and releases ADH (vasopressin) and Oxytocin. --- A. HYPERPITUITARISM This condition is most commonly caused by a functioning pituitary adenoma . Pituitary Adenomas These are benign tumors of anterior pituitary cells, classified by size ( 1 cm = macroadenoma ) and the hormone they secrete. Adenoma Type Hormone Clinical Syndrome --- --- --- Somatotroph GH Gigantism (children) / Acromegaly (adults) Lactotroph (most common) Prolactin Hyperprolactinemia Corticotroph ACTH Cushing disease Thyrotroph TSH Hyperthyroidism Gonadotroph FSH/LH Usually non-functioning Null cell None Mass effects only Mass Effects of Pituitary Adenoma Compression by a pituitary adenoma can lead to bitemporal hemianopia (due to compression of the optic chiasm), headache, hypopituitarism, and cranial nerve palsies (III, IV, VI) if the cavernous sinus is invaded. --- 1. Hyperprolactinemia The most common functioning pituitary adenoma is the prolactinoma. - Causes: Prolactinoma, drugs (dopamine antagonists, opioids), hypothyroidism, stalk compression, and physiological states (pregnancy, breastfeeding). - Effects: In women, it causes galactorrhea, amenorrhea, and infertility . In men, it can lead to impotence, decreased libido, infertility, and gynecomastia. - Treatment: Dopamine agonists like bromocriptine and cabergoline. 2. Growth Hormone Excess - Gigantism results from excess GH before epiphyseal closure, leading to excessive linear growth. - Acromegaly occurs when excess GH is present after epiphyseal closure. Features include enlarged hands and feet, coarse facial features, prognathism, macroglossia, and increased hat/shoe/ring size. Organomegaly (cardiomegaly, hepatomegaly), carpal tunnel syndrome , arthritis, diabetes mellitus (due to GH's anti-insulin effects), hypertension, and increased cancer risk are also associated. - Diagnosis: Elevated IGF-1 levels and lack of GH suppression by an oral glucose tolerance test. 3. ACTH Excess (Cushing Disease) A pituitary ACTH-secreting adenoma causes bilateral adrenal hyperplasia and excess cortisol, leading to Cushing disease. This is discussed further under Adrenal section. --- B. HYPOPITUITARISM Definition This is the deficiency of one or more anterior pituitary hormones. Causes The most common cause is a pituitary adenoma compressing normal tissue. Other causes include Sheehan syndrome (postpartum pituitary necrosis), craniopharyngioma, traumatic brain injury, radiation, empty sella syndrome, granulomas, and hemochromatosis. Clinical Effects (order of loss — GH lost first) The hormones are typically lost in a specific order: 1. GH deficiency : Growth failure in children; fatigue and reduced muscle mass in adults. 2. FSH/LH deficiency : Hypogonadism, infertility, amenorrhea, and decreased libido. 3. TSH deficiency : Secondary hypothyroidism. 4. ACTH deficiency : Secondary adrenal insufficiency (without hyperpigmentation). 5. Prolactin deficiency : Failure to lactate postpartum. Panhypopituitarism This is the deficiency of all anterior pituitary hormones and can be a medical emergency if acute. --- C. POSTERIOR PITUITARY DISORDERS Diabetes Insipidus (DI) This condition is characterized by the deficiency of ADH action , leading to an inability to concentrate urine and resulting in polyuria (large volumes of dilute urine) and polydipsia . - Types: - Central DI : Decreased ADH production (causes: head trauma, surgery, tumors, Sheehan syndrome, idiopathic). Treatment: desmopressin (DDAVP) . - Nephrogenic DI : Kidneys do not respond to ADH (causes: lithium, hypercalcemia, hypokalemia, genetic factors). Treatment: thiazides, low-salt diet. - Diagnosis: Water deprivation test followed by a response to desmopressin. - Lab findings: Low urine osmolality, high serum osmolality, and hypernatremia. Syndrome of Inappropriate ADH (SIADH) This involves excess ADH , leading to excessive water retention and dilutional hyponatremia . - Causes: CNS disorders (meningitis, stroke, head trauma), pulmonary conditions (pneumonia, TB), malignancy (Small cell carcinoma of the lung) , drugs (carbamazepine, SSRIs), hypothyroidism, and Addison disease. - Lab findings: Low serum sodium, low serum osmolality, inappropriately concentrated urine (urine osmolality serum osmolality), and high urine sodium. - Symptoms: Nausea, confusion, seizures, and coma due to cerebral edema. - Treatment: Fluid restriction; hypertonic saline for severe cases; demeclocycline or tolvaptan. --- TOPIC 2: THYROID DISORDERS Normal Thyroid Function The thyroid gland produces T3 (active) and T4 (prohormone), regulated by TSH from the pituitary, which is in turn regulated by TRH from the hypothalamus. T3 and T4 increase metabolic rate, protein synthesis, cardiac output, and gut motility. --- A. GOITER Definition A goiter is an enlargement of the thyroid gland , regardless of its cause. Types 1. Diffuse Non-toxic Goiter (Simple/Colloid Goiter) This is a generalized, smooth thyroid enlargement in euthyroid individuals. - Causes: Iodine deficiency (most common worldwide) and goitrogens (e.g., cabbage, cassava). - Mechanism: Low T3/T4 leads to increased TSH, causing thyroid hyperplasia and goiter. - Histology: Follicles are distended with colloid, and the follicular epithelium is flattened. 2. Multinodular Goiter This results from long-standing simple goiter with uneven hyperplasia leading to nodules. It can be toxic (causing hyperthyroidism) or non-toxic and may cause tracheal or esophageal compression. Plummer syndrome refers to toxic multinodular goiter, where autonomous nodules produce excess T3/T4. --- B. HYPOTHYROIDISM Definition A deficiency of thyroid hormone, leading to a decreased metabolic rate . Primary vs Secondary - Primary hypothyroidism originates in the thyroid gland (high TSH, low T4). - Secondary hypothyroidism originates in the pituitary (low TSH, low T4). Causes of Primary Hypothyroidism The most common cause in iodine-sufficient areas is Hashimoto thyroiditis . Other causes include iodine deficiency, post-radioiodine therapy or thyroidectomy, certain drugs, and congenital hypothyroidism (cretinism). Clinical Features Hypothyroidism causes a slowing of all metabolic processes, including cold intolerance, weight gain, fatigue, constipation, bradycardia, and hypertension (diastolic). Myxedema —non-pitting edema due to glycosamin