Pituitary Gland Medium

• The pituitary gland, often called the "master gland," is located on the inferior aspect of the brain and controls hormone secretion by other endocrine glands.
• It is divided into anterior and posterior lobes and is controlled by the hypothalamus via the pituitary stalk.

Anterior Pituitary

• Major hormones include FSH, LH, prolactin (PRL), ACTH, TSH, and GH (somatotropin).
• Secretion is controlled by releasing factors from the hypothalamus, which reach the anterior pituitary via the pituitary portal blood system.
• Melanocyte-stimulating hormone and beta-lipotropin are also produced
• TSH, ACTH, FSH, and LH primarily stimulate hormone release from other endocrine glands.
• Imbalanced ACTH secretion leads to Addison’s disease (hypoproduction) or Cushing’s syndrome (hyperproduction).
• Prolactin (PRL) stimulates milk production in the breasts.
• GH regulates growth in children and energy and metabolism in adults by increasing protein synthesis, breaking down fatty acids, and increasing blood glucose levels.
• GH secretion is increased by deep sleep, stress, exercise, fasting, malnutrition, hypoglycemia, trauma, hypovolemic shock, and sepsis.
• GH secretion is decreased by obesity, depression, and hypothyroidism.

Posterior Pituitary

• Secretes vasopressin (ADH) and oxytocin, which are synthesized in the hypothalamus and stored in the posterior pituitary.
• Vasopressin controls water excretion by the kidneys and is stimulated by increased blood osmolality or decreased blood pressure.
• Oxytocin secretion is stimulated during pregnancy and childbirth.
• Oxytocin helps with milk ejection during lactation and increases uterine contractions during labor and delivery.

Pathophysiology of Pituitary Gland

• Abnormal pituitary function results from over- or undersecretion of hormones.
• Anterior and posterior pituitary abnormalities can occur independently.
• Hypopituitarism is caused by disease of the pituitary gland or hypothalamus and can result from radiation therapy.
• Destruction of the pituitary gland leads to loss of stimuli to the thyroid, gonads, and adrenal glands.
• Untreated hypopituitarism can lead to extreme weight loss, atrophy of endocrine glands, hair loss, impotence, amenorrhea, hypometabolism, and hypoglycemia, potentially leading to coma and death.

Anterior Pituitary Dysfunction

• Oversecretion of ACTH results in Cushing’s syndrome
• Oversecretion of GH in adults causes acromegaly, leading to enlargement of peripheral body parts and soft tissue after epiphyseal plate fusion.
• Oversecretion of GH in children results in pituitary gigantism.
• Insufficient GH secretion in children leads to pituitary dwarfism.
• Undersecretion of all anterior pituitary hormones is termed panhypopituitarism, causing atrophy of the thyroid gland, adrenal cortex, and gonads.

Posterior Pituitary Dysfunction

• The most common disorder is diabetes insipidus (DI), marked by excretion of large volumes of dilute urine due to deficient vasopressin production.
• DI can result from surgical treatment of a brain tumor, nonsurgical brain tumors, traumatic brain injury, infections, post-hypophysectomy, failure of renal tubules to respond to ADH, and certain medications.

Pituitary Tumors

• Most pituitary tumors are benign and slow-growing.
• Tumors can be primary or secondary, and functional (secreting hormones) or nonfunctional.
• Tumors cause clinical issues due to pressure on adjoining tissues, endocrine dysfunction, or dysfunctional effects on target organs.
• Pituitary tumors are classified based on cell type: eosinophilic, basophilic, or chromophobic.

Clinical Manifestations of Pituitary Tumors

• Eosinophilic tumors in early life lead to gigantism.
• Eosinophilic tumors in adulthood lead to acromegaly, with skeletal growth in the feet, hands, superciliary ridge, nose, and chin.
• Acromegaly can cause severe headaches and visual disturbances due to pressure on the optic nerves.
• Basophilic tumors cause Cushing’s syndrome, with features like masculinization, amenorrhea, truncal obesity, hypertension, osteoporosis, and polycythemia.
• Chromophobic tumors (90% of pituitary tumors) typically cause hypopituitarism.
• Chromophobic tumors can lead to obesity, somnolence, fine hair, dry skin, headaches, loss of libido, visual defects, polyuria, polyphagia, lowered basal metabolic rate, and subnormal body temperature.

Diagnosis and Assessment

• Requires careful history and physical examination, including assessment of visual acuity and visual fields.
• CT and MRI scans diagnose the presence and extent of pituitary tumors.
• Serum levels of pituitary hormones and target organ hormones are measured to assist in diagnosis.

Medical Management

• Hypophysectomy is the usual treatment, performed via a transsphenoidal approach.
• Stereotactic radiation therapy delivers precise radiation to the pituitary tumor.
• Other treatments include conventional radiation therapy, bromocriptine, and octreotide.
• Octreotide and lanreotide may improve symptoms and shrink tumors preoperatively.

Surgical Management

• Hypophysectomy is the treatment of choice for Cushing’s disease resulting from excessive ACTH production.
• It may also be performed to relieve bone pain secondary to metastasis of breast and prostate lesions.
• Surgical approaches include transfrontal, subcranial, or oronasal–transsphenoidal approaches; irradiation; and cryosurgery.
• The absence of the pituitary gland alters the function of many body systems.
• Menstruation ceases and infertility occurs after pituitary ablation.
• Replacement therapy with corticosteroids and thyroid hormone is necessary.

Diabetes Insipidus (DI)

• Rare disorder due to injury to the hypothalamus or pituitary gland with a deficiency of ADH (vasopressin) leading to excretion of large volumes of dilute urine and extreme thirst.
• DI can be central, nephrogenic, dipsogenic, or gestational.
• Central DI is primarily caused by head trauma, surgery, infection, inflammation, brain tumors, or cerebral vascular disease
• Nephrogenic DI is caused by kidney injury, medications like lithium, hypokalemia, and hypercalcemia.
• Dipsogenic DI is caused by a defect in the hypothalamus and may result from damage to the pituitary gland.
• DI must be differentiated from diabetes, which may also cause polydipsia and excessive urination.

Clinical Manifestations of DI

• Enormous daily output (greater than 250 mL per hour) of very dilute urine with a specific gravity of 1.001 to 1.005.
• Urine contains no abnormal substances.
• Intense thirst leads to drinking 2 to 20 L of fluid daily, with a craving for cold water.
• Onset may be insidious or abrupt.
• Fluid restriction cannot control the disease and leads to an insatiable craving for fluid, hypernatremia, and severe dehydration.

Diagnosis and Assessment of DI

• The fluid deprivation test involves withholding fluids for 8 to 12 hours or until 3% to 5% of body weight is lost.
• Plasma and urine osmolality studies are performed at the beginning and end of the test.
• The inability to increase the specific gravity and osmolality of the urine is characteristic of DI.
• Other diagnostic procedures include concurrent measurements of plasma levels of ADH and plasma and urine osmolality as well as a trial of desmopressin therapy.

Medical Management of DI

• Replace ADH, ensure adequate fluid replacement, and identify and correct the underlying intracranial pathology.
• Nephrogenic causes require different management approaches.
• Desmopressin is the drug of choice for central DI and can be given orally or intranasally.
• Chlorpropamide and thiazide diuretics are used in mild forms of the disease but are used with caution due to the risk for hypoglycemia.
• Thiazide diuretics, mild salt depletion, and prostaglandin inhibitors are used to treat the nephrogenic form of DI.

Nursing Management of DI

• Ongoing physical assessment and patient education are crucial.
• Monitor for clinical manifestations of dehydration.
• Educate the patient and family about follow-up care, prevention of complications, and emergency measures.
• Provide specific instructions on medication dose, actions, side effects, and administration.
• Advise the patient to wear a medical identification bracelet and carry required medication and information about DI at all times.

Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)

• Results from a failure of the negative feedback system that regulates ADH release.
• Patients with SIADH cannot excrete dilute urine, retain fluids, and develop dilutional hyponatremia.
• Causes include bronchogenic carcinoma, severe pneumonia, pneumothorax, disorders of the lungs, malignant tumors, disorders of the central nervous system, and some medications.

Medical Management of SIADH

• Focuses on eliminating the underlying cause and restricting fluid intake.
• Diuretic agents such as furosemide may be used along with fluid restriction.
• In severe hyponatremia, hypertonic NaCl (3%) may be prescribed and administered IV.

Nursing Management of SIADH

• Closely monitor fluid I&O, daily weight, urine and blood chemistries, and neurologic status.
• Provide supportive measures and explanations of procedures and treatments to assist the patient in managing the disorder.