Comprehensive Study Guide for the Endocrine System

Learning Competencies and Course Information

• Course: NURS112M: The Endocrine System

• Instructor: Professor Perrotta, MSN, RN

• Key Objectives:

  • Describe endocrine gland functions and hormones, as well as associated diseases of dysfunction.

  • Identify diagnostic tests for alterations in endocrine function.

  • Explain pharmacotherapy for antidiuretic hormone (ADH) disorders.

  • Discuss nursing management for patients with common endocrine regulation problems.

  • Outline the nursing plan of care for patients undergoing a thyroidectomy.

  • Identify teaching needs for patients on corticosteroid therapy.

  • Compare Addison’s disease and Cushing’s syndrome (causes, manifestations, and interventions).

  • Describe adverse effects of long-term corticosteroid use.

  • Describe assessment, medical care, and nursing interventions for thyroid disorders.

  • Discuss the psychosocial effects of endocrine disorders.

Anatomy and Physiology of the Endocrine System

• Major Endocrine Glands:

  • Hypothalamus: The control center located in the brain.

  • Pituitary Gland: Often called the "master gland," about the size of a pea, located below the hypothalamus.

  • Pineal Gland: Located in the brain.

  • Thyroid Gland: A vascular organ in the neck with two lobes flanking the trachea.

  • Parathyroid Glands: Embedded within the thyroid gland.

  • Thymus: Located in the upper chest.

  • Pancreas: Involved in glucose regulation.

  • Adrenal Glands: Located on top of the kidneys (Cortex and Medulla).

  • Gonads: Ovaries (female) and Testicles (male).

  • Placenta: Functions as an endocrine organ during pregnancy.

The Pituitary Gland: Master Regulator

• Anatomy: Located near the cerebrum, cerebellum, and brain stem. Controlled by the hypothalamus.

• Hormones Secreted and Target Organs:

  • MSH (Melanocyte-Stimulating Hormone): Targets the skin.

  • ACTH (Adrenocorticotropic Hormone): Targets the adrenal cortex to stimulate cortisol production.

  • Prolactin: Targets the breast for milk production.

  • Oxytocin: Targets the breast and uterus.

  • ADH (Antidiuretic Hormone): Targets the kidneys to regulate water retention.

  • Gonadotropins (FSH/LH): Target the ovaries and testicles.

  • GH (Growth Hormone): Targets bones and muscles.

  • TSH (Thyroid-Stimulating Hormone): Targets the thyroid gland.

Pituitary Conditions and Growth Disorders

• General Conditions: Hyperpituitarism, Hypopituitarism, Pituitary Tumors, Cushing’s Disease, Hyperprolactinemia, and Traumatic Brain Injury (TBI).

• Growth Hormone (GH) Disorders:

  • Growth Hormone Deficiency (Pituitary Dwarfism): Hyposecretion of GH during childhood.

  • Gigantism: Hypersecretion of GH during childhood before the closure of epiphyseal growth plates; results in abnormally high linear growth.

  • Acromegaly: Hypersecretion of GH (disorder of $IGF\text{-}1$) occurring in adulthood after growth plates have closed. Characterized by excessive growth of hands, feet, jaw, and internal organs.

• Diagnosis of Acromegaly:

  • MRI: Shows a pituitary tumor in $90\%$ of acromegalic patients.

  • Oral Glucose Suppression Test: The best confirmatory test. In normal individuals, glucose suppresses GH; in acromegaly, glucose does not suppress GH.

ADH Disorders: SIADH vs. Diabetes Insipidus (DI)

• SIADH (Syndrome of Inappropriate Antidiuretic Hormone):

  • Pathophysiology: Hypersecretion of ADH leading to excessive water reabsorption by the kidneys.

  • Result: Hemodilution, dilutional hyponatremia ($low\,Na^+$), and fluid volume overload.

  • Symptoms: Decreased urination, concentrated urine in small amounts, water intoxication, cerebral edema (expanding brain cells), headache, altered Level of Consciousness (LOC), and seizures.

  • Treatment: Long-term fluid restriction, diuretics, monitoring electrolytes ($K^+$), strict I&O, neurological exams, assessment of lung sounds/hydration, and IV hypertonic saline for symptomatic low $Na^+$ levels.

• Diabetes Insipidus (DI):

  • Pathophysiology: Hyposecretion of ADH or kidney resistance to ADH leading to "too little water" in the body.

  • Clinical Presentation: Extreme thirst (polydipsia), craving for cold/iced water, and excessive urination (polyuria) ranging from $2\text{-}20\,L$ in $24\,h$.

  • Urine: Massively dilute with a low specific gravity ($1.001\text{-}1.005$).

  • Serum: Concentrated with hypernatremia ($high\,Na^+$) and dehydration.

  • Types:

    1. Central DI: Decreased ADH secretion due to idiopathic causes, head trauma, pituitary tumors, or neurosurgery.

    2. Nephrogenic DI: Kidney resistance to ADH caused by lithium toxicity, renal disease, hypokalemia ($low\,K^+$), pregnancy, or certain medications.

  • DI Treatment: No fluid restriction, careful I&O monitoring, daily weights, skin turgor and mucous membrane assessment, and antidiuretic replacement (Desmopressin/synthetic ADH).

  • Note: Desmopressin controls neurogenic DI but not nephrogenic DI; it carries a risk of water intoxication and hyponatremia.

Parathyroid Gland Function and Disorders

• Function: Secretes Parathyroid Hormone (PTH) to regulate blood calcium levels.

• Hypoparathyroidism:

  • Characteristics: Low PTH levels leading to low blood calcium and high phosphorus levels.

  • Signs: Tetany, Trousseau sign, Chvostek sign, and Paresthesia (abnormal sensations such as tingling, pricking, or numbness).

  • Treatment: Lifelong calcium ($Ca^+$) supplements.

• Hyperparathyroidism:

  • Cause: Usually a benign tumor; cured by surgical removal.

  • Signs: High serum calcium, kidney stones, osteoporosis, and neurological changes (depression, agitation, lack of energy).

  • Nursing Interventions: Increase oral fluid intake to >2\,L/day to prevent renal calculi, maintain accurate I&O, provide a low-calcium diet, and encourage cranberry juice to acidify urine (decreasing calculus formation). Avoid high-calcium antacids. Post-surgery, monitor for signs of hypocalcemia.

Thyroid Gland Physiology and Hormones

• Anatomy: Highly vascular, located in the neck with two lobes on either side of the trachea.

• Control: Regulated by the pituitary gland via TSH.

• Hormones:

  • $T_4$ (Thyroxine) and $T_3$ (Triiodothyronine).

  • TSH (Thyroid Stimulating Hormone): Controls the rate of thyroid hormone release.

• Iodine Role: Thyroid cells are the only cells in the body that absorb iodine. Iodine combines with tyrosine to create $T_3$ and $T_4$.

  • Iodine-Rich Foods: Spinach, lentils, figs, kidney beans, quinoa, potatoes, oats, and soybeans.

Hyperthyroidism (Graves’ Disease)

• Pathophysiology: Autoimmune disease resulting in high levels of $T_4$/$T_3$ and low TSH levels.

• Clinical Manifestations: Intolerance to heat, fine straight hair, bulging eyes (Exophthalmos), facial flushing, enlarged thyroid (Goiter), tachycardia, increased systolic blood pressure, breast enlargement, weight loss, muscle wasting, tremors, diarrhea, amenorrhea, localized edema, and finger clubbing.

• Diagnostic Testing:

  • TSH: Low level ($0.5\text{-}5.0\,mililU/L$ is normal range; values will be lower).

  • $T_4$: High levels ($normal: 4\text{-}12\,mcg/dL$).

  • $T_3$: High levels ($normal: 10\text{-}26\,mcg/dL$).

  • Radioactive Iodine Uptake Test (RAIU): Measures iodine absorption; results are altered by iodine-rich foods/meds.

  • Thyroid Scan and visual/palpation assessment.

• Treatment:

  • Medications: methimazole (Tapazole) and propylthiouracil (PTU). PTU is preferred for having fewer teratogenic effects.

  • Radioisotope Therapy: Radioactive drug compound destroys thyroid cells (medical thyroidectomy). Symptoms decrease in $6\text{-}8\,weeks$. Most patients eventually develop hypothyroidism. Patients must avoid contact with children/pregnant women for one week post-treatment.

  • Surgery: Thyroidectomy.

• Thyrotoxic Storm: Acute, life-threatening emergency. Characterized by high fever, tachycardia, altered mental status, and exaggerated hyperthyroid symptoms. Treated with supportive care, antithyroid drugs, iodine, and beta-blockers.

Hypothyroidism (Hashimoto’s Disease)

• Pathophysiology: Insufficient secretion of thyroid hormones leading to a slowed metabolism.

• Causes: Autoimmune (Hashimoto’s thyroiditis), post-hyperthyroid treatment, pituitary disease, or severe iodine deficiency.

• Clinical Manifestations: Intolerance to cold, receding hairline, facial/eyelid edema, dull blank expression, extreme fatigue, thick tongue, slow speech, anorexia, brittle nails/hair, menstrual disturbances, hair loss, apathy, lethargy, dry skin, muscle aches, weakness, constipation, weight gain, bradycardia, and decreased LOC (late sign).

• Treatment: Thyroid hormone replacement with levothyroxine sodium (Synthroid).

  • Testing: High TSH with low $T_4$ and $T_3$.

• Levothyroxine Education:

  • Long-term use is associated with osteoporosis.

  • Increases the effects of warfarin.

  • May decrease the effects of beta-blockers.

  • Timing: Calcium or iron supplements must be taken at least $4\,hours$ after levothyroxine to avoid interference with drug absorption.

Goiters and Thyroid Cancer

• Goiter: A non-cancerous enlargement of the thyroid gland.

  • Causes: Hyper/hypothyroidism, tumors, autoimmune disease, hormonal changes, lithium, or smoking.

  • Symptoms: Swelling/tightness in the neck, breathing/swallowing difficulties, coughing, wheezing, or hoarseness.

  • Nursing Actions: Assess emotional response, dyspnea, dysphagia, and food/fluid intake.

• Thyroid Cancer:

  • Signs: Often an asymptomatic mass. Rare signs include cough, dyspnea, dysphagia, pain, stridor, vocal cord paralysis, or rapid enlargement.

  • Surgical Options: Lobectomy (partial) or Thyroidectomy (entire gland removed). Nearby lymph nodes may be removed if cancer has spread.

Nursing Care Post-Thyroidectomy

• Critical Monitoring: Watch for tracheal edema, airway occlusion, hemorrhage, hypoparathyroidism, and vocal cord paralysis.

• Assessment: Check patient's speech for laryngeal nerve damage. Assess for hypocalcemia/tetany using Trousseau’s and Chvostek’s signs.

• Emergency Resource: Keep IV calcium gluconate available.

• Nursing Diagnoses: Impaired Comfort, Risk for Ineffective Airway Clearance, and Impaired Verbal Communication.

Adrenal Gland Anatomy and Hormones

• Structure: Adrenal Cortex (outer) and Adrenal Medulla (inner).

• Adrenal Cortex Hormones (SSS - Sugar, Salt, Sex):

  1. Glucocorticoids (Sugar): Cortisol and Cortisosteron. Regulated by ACTH from the pituitary.

  2. Mineralocorticoids (Salt): Aldosterone and Corticosterone. Regulated by the Zona glomerulosa.

  3. Androgens (Sex): Estrogens and Testosterone. Regulated by the Zona reticularis.

• Adrenal Medulla Hormones: Catecholamines (Epinephrine and Norepinephrine).

• Other Hormones: Peptides like Somatostatin and Substance P.

• Cortisol Feedback Loop: Rising cortisol levels signal the pituitary gland to decrease ACTH production.

Adrenal Insufficiency and Addison’s Disease

• Primary AI (Addison’s Disease): Damaged adrenal glands lead to decreased production of all adrenal hormones, compromising stress response and increasing infection risk.

• Secondary AI: Failure of the pituitary to produce ACTH, leading to adrenal atrophy. This is more common than Addison’s.

• Manifestations: Bronze pigmentation of skin, changes in body hair distribution, GI disturbances, weakness, hypoglycemia, postural hypotension, and weight loss.

• Acute Adrenal Crisis (Addisonian Crisis): Life-threatening emergency caused by a lack of cortisol often after infection, trauma, or abrupt withdrawal of steroids.

  • Signs: Shock, dehydration, hypotension, hyponatremia ($low\,Na^+$), hyperkalemia ($high\,K^+$), and loss of consciousness.

  • Interventions: Immediate IV/IM hydrocortisone, IV fluids for vascular collapse, vasopressors for BP support, and antibiotics for infection.

• Sick Day Rules for AI:

  • Rule 1: Double daily oral glucocorticoid dose for illness with fever, bedrest, or antibiotics.

  • Rule 2: Administer via IV/IM injection for prolonged vomiting, diarrhea, colonoscopy prep, or acute trauma/surgery.

Cushing’s Disease vs. Cushing’s Syndrome

• Both: Result from excessive cortisol levels.

• Cushing’s Disease: Caused by a pituitary tumor producing too much ACTH.

• Cushing’s Syndrome: Caused by factors outside the body, primarily long-term corticosteroid medication use.

• Clinical Manifestations: Moon face (red face), Buffalo hump, personality changes, susceptibility to infection, hyperglycemia, fluid retention (edema), thin extremities, GI distress (increased acid), purple striae, osteoporosis, thin skin, and bruises/petechiae.

  • Males: Gynecomastia.

  • Females: Amenorrhea and Hirsutism.

• Treatment: Hypophysectomy (pituitary removal), radiation, adrenalectomy (requires lifetime hormone replacement if bilateral), or tapering of corticosteroids.

Glucocorticoid Therapy

• Actions: Stops the inflammatory process, stimulates glucose production, and curbs glucose storage in cells.

• Side Effects: Immunosuppression, hyperglycemia, weight gain, easy bruising, reduced bone density, muscle breakdown/weakness, cataracts, glaucoma, and adrenal insufficiency if stopped suddenly.

• Patient Education: Administer in the early morning; never discontinue suddenly; increase doses during times of stress.