Anterior & Posterior Pituitary Gland PDF

# Anterior Pituitary Gland ## I. Pituitary Adenoma - Benign tumor of anterior pituitary cells - May be functional (hormone-producing) or nonfunctional (silent) - **Nonfunctional tumors** often present with mass effect - Bitemporal hemianopsia occurs due to compression of the optic chi...

# Anterior Pituitary Gland ## I. Pituitary Adenoma - Benign tumor of anterior pituitary cells - May be functional (hormone-producing) or nonfunctional (silent) - **Nonfunctional tumors** often present with mass effect - Bitemporal hemianopsia occurs due to compression of the optic chiasm - Hypopituitarism occurs due to compression of normal pituitary tissue - Headache - **Functional tumors** present with features based on the type of hormone produced. ## C. Prolactinoma - Presents as galactorrhea and amenorrhea (females) or as decreased libido and headache (males); most common type of pituitary adenoma - Treatment is dopamine agonists (e.g., bromocriptine or cabergoline) to suppress prolactin production (shrinks tumor) or surgery for larger lesions. ## D. Growth hormone cell adenoma - Gigantism in children - increased linear bone growth (epiphyses are not fused) - Acromegaly in adults - Enlarged bones of hands, feet, and jaw - Growth of visceral organs leading to dysfunction (e.g., cardiac failure) - Enlarged tongue - Secondary diabetes mellitus is often present (GH induces liver gluconeogenesis). - Diagnosed by elevated GH and insulin growth factor-1 (IGF-1) levels along with lack of GH suppression by oral glucose - Treatment is octreotide (somatostatin analog that suppresses GH release), GH receptor antagonists, or surgery. ## E. ACTH cell adenomas - Secrete ACTH leading to Cushing syndrome (see "Adrenal Cortex" below). ## F. TSH cell, LH-producing, and FSH-producing adenomas - Occur, but are rare. # II. Hypopituitarism - Insufficient production of hormones by the anterior pituitary gland - Symptoms arise when >75% of the pituitary parenchyma is lost. ## B. Causes include - Pituitary adenomas (adults) or craniopharyngioma (children) - due to mass effect or pituitary apoplexy (bleeding into an adenoma) - Sheehan syndrome - pregnancy-related infarction the of pituitary gland - Gland doubles in size during pregnancy, but blood supply does not increase significantly; blood loss during parturition precipitates infarction. - Presents as poor lactation, loss of pubic hair, and fatigue - Empty sella syndrome - congenital defect of the sella - Herniation of the arachnoid and CSF into the sella compresses and destroys the pituitary gland. - Pituitary gland is "absent" (empty sella) on imaging. # Posterior Pituitary Gland ## I. Basic Principles - Antidiuretic hormone (ADH) and oxytocin are made in the hypothalamus and then transported via axons to the posterior pituitary for release. - ADH acts on the distal tubules and collecting ducts of the kidney to promote free water retention. - Oxytocin mediates uterine contraction during labor and release of breast milk (let-down) in lactating mothers. ## II. Central Diabetes Insipidus - ADH deficiency - Due to hypothalamic or posterior pituitary pathology (e.g., tumor, trauma, infection, or inflammation) - Clinical features are based on loss of free water. - Polyuria and polydipsia with risk of life-threatening dehydration - Hypernatremia and high serum osmolality - Low urine osmolality and specific gravity - Water deprivation test fails to increase urine osmolality (useful for diagnosis). - Treatment is desmopressin (ADH analog). ## III. Nephrogenic Diabetes Insipidus - Impaired renal response to ADH - Due to inherited mutations or drugs (e.g., lithium and demeclocycline) - Clinical features are similar to central diabetes insipidus, but there is no response to desmopressin. ## IV. Syndrome of Inappropriate ADH (SIADH) Secretion - Excessive ADH secretion - Most often due to ectopic production (e.g., small cell carcinoma of the lung); other causes include CNS trauma, pulmonary infection, and drugs (e.g., cyclophosphamide). - Clinical features are based on retention of free water - Hyponatremia and low serum osmolality - Mental status changes and seizures - Hyponatremia leads to neuronal swelling and cerebral edema. - Treatment is free water restriction or demeclocycline.