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ENDOCRINE SYSTEM STUDY NOTES

Objectives For This Lecture

• Review the pathophysiology, presentation, diagnostics, and nursing care for the following conditions:
    - Acromegaly (Growth Hormone)
    - SIADH (Syndrome of Inappropriate Antidiuretic Hormone)
    - Diabetes Insipidus (ADH Deficiency)
    - Hyperthyroidism and Hypothyroidism (Thyroid Hormone)
    - Hyperparathyroidism and Hypoparathyroidism (Parathyroid Hormone)
    - Cushing's Syndrome and Addison’s Disease (Adrenal Hormones)
    - Hyperaldosteronism (Aldosterone)
    - Pheochromocytoma (Catecholamines)

Structures and Functions

• Endocrine Organs: Organs of the endocrine system that secrete hormones
• Hormones: Chemical substances produced by endocrine glands
• Target Tissue: The body tissue or organ that the hormone affects
• Close relationship between the hypothalamus and pituitary gland, which coordinate the activity of the endocrine system.

Feedback Mechanisms

• Input: Stimulus
• Process: Action of the system
• Output: Response
• Feedback: Mechanisms that promote homeostasis in the body via negative feedback loops.
    - Example: If a room warms up, the air conditioner turns on, inhibiting temperature increase. Subsequent cooling turns the AC off.

Thyroid Gland

• Hormones:
    - T3 (Triiodothyronine): More potent form of thyroid hormone.
    - T4 (Thyroxine): Approx. 90% of thyroid hormone produced.
    - Calcitonin: Lowers serum calcium levels; works with parathyroid hormones to regulate calcium balance.

Parathyroid Gland

• Secretes Parathyroid Hormone (PTH): Raises serum calcium levels, works with calcitonin for calcium homeostasis.
• Feedback Cycle:
    - If serum calcium increases, PTH secretion decreases; if it decreases, PTH secretion increases.

Adrenal Glands

• Medulla (Inner portion): Secretes:
    - Epinephrine and Norepinephrine (Catecholamines)
• Cortex (Outer portion): Secretes:
    - Glucocorticoids (e.g., cortisol)
    - Mineralocorticoids (e.g., aldosterone)
    - Androgens (e.g., sex hormones)

Endocrine Dysfunction

• Typically occurs due to an imbalance (excess or deficiency) of hormones.
• Can cause gradual onset of symptoms; comprehensive history and physical exam are necessary.
    - Key areas of focus:
      - Secondary sexual characteristics
      - Heredity
      - Energy levels
      - Changes in physical appearance (skin, weight)
• Diagnosing endocrine disorders can be challenging.

PITUITARY GLAND (ANTERIOR)

Acromegaly

• Definition: Excess growth hormone (GH), often due to a pituitary adenoma.
• Role of GH:
    - Promotes growth in children until epiphyseal plates close.
    - Maintains metabolism in adults (blood glucose levels).
• Characteristics:
    - Rare but reduces life expectancy.
    - Mean age of onset is around 40-45 years.
    - Slow progression leads to overgrowth of bones and soft tissues.

Signs & Symptoms of Acromegaly

• Early Symptoms:
    - Enlargement of tongue and nasal bone
• Other Symptoms:
    - Protruding brow and lower jaw
    - Thick and oily skin
    - Swollen hands and feet

Complications

• Untreated Acromegaly may lead to:
    - Sleep apnea
    - Visual problems and headaches
    - Diabetes mellitus
    - Cardiovascular disease

Diagnostics

• Tests for Acromegaly:
    - IGF-1 Levels: As GH levels increase, IGF-1 levels increase.
    - Growth Hormone Levels: Obtained during an oral glucose tolerance test; no change in GH levels indicates acromegaly.
    - Imaging: CT or MRI to detect pituitary tumor.

Surgical Intervention

• Transsphenoidal Hypophysectomy: Surgical removal of the tumor, considered the treatment of choice.
     - Post-op Nursing Care:
       - Neurological assessments
       - Monitoring for CSF leaks
       - Positioning of the head at 30° and other considerations regarding urine output.

PITUITARY GLAND (POSTERIOR)

Disorders

• Syndrome of Inappropriate Antidiuretic Hormone (SIADH):
    - Excess of ADH leads to water retention in the body.

• Diabetes Insipidus (DI):
    - Deficit of ADH results in excessive urination and dehydration.

Action of Antidiuretic Hormone (ADH)

• Increases water reabsorption in the kidneys and thus increases blood volume, leading to elevated blood pressure.

SIADH

• Signs:
    - Fluid retention
    - Hyponatremia (low sodium levels) due to dilutional effect
    - Neuro symptoms due to decreased serum sodium

Symptoms of SIADH

• Weight gain, fluid overload, dyspnea, confusion, seizures, coma.

Diagnostics for SIADH

• Conduct tests for serum sodium, urine sodium, serum osmolality, urine osmolality, and specific gravity of urine.

Outcomes of SIADH Management

• Fluid restriction, hypertonic sodium chloride solution to raise serum sodium, and loop diuretics if necessary.

Diabetes Insipidus (DI)

Definition

• ADH deficiency characterized by excessive urination (polyuria) and thirst (polydipsia).

Types of DI

• Central DI: True ADH deficit due to hypothalamic or pituitary issues; often from head injury or surgery.
• Nephrogenic DI: Kidneys' inability to respond to ADH despite its presence.

Symptoms of DI

• Increased urine output, dehydration signs, hypernatremia.

Diagnostics for DI

• Serum and urine sodium, osmolality, specific gravity evaluations.

Management of DI

• Fluid replacement, medications like desmopressin for central DI, and monitoring hydration and electrolytes.

Comparison: SIADH vs. DI

THYROID GLAND

Function of Thyroid Hormones

• Control metabolism, influence heart rate, blood pressure, body temperature, and are crucial for bone growth and brain development.

Thyroid Disorders

• Hyperthyroidism and Hypothyroidism characteristics and presentations:
    - Hyperthyroidism: Symptoms include: increased HR, appetite, and weight loss; anxiety, insomnia, goiter.
    - Hypothyroidism: Symptoms include: decreased HR, appetite; weight gain, fatigue, mental slowing.

Nutritional Considerations for Hyperthyroidism

• Patients require a high-calorie and protein diet; foods high in iodine should be avoided.

Diagnostic Tests for Thyroid Disorders

• Serum TSH, T3, T4 levels; radioactive iodine uptake tests; specific gravity evaluations for urine.

MYXEDEMA COMA

Definition

• Severe hypothyroidism characterized by profound slowing of body processes; potential 30-50% mortality rate.

Symptoms of Myxedema Coma

• Severe low heart rate, low blood pressure and hypothermia, confusion, and altered mental status.

Nursing Care

• Monitoring vital signs, administering thyroid hormone replacement, vital control, and managing fluids.

HYPERPARATHYROIDISM

Definition

• Overproduction of parathyroid hormone (PTH), often due to benign tumors; causes hypercalcemia.

Symptoms

• Gastrointestinal disturbances, neuromuscular issues, increased fractures, polydipsia, and mental changes.

Management

• Monitor calcium levels, symptoms, and assess for surgery if necessary.

HYPOSYPARATHYROIDISM

Symptoms & Management

• Hypotension, dysrhythmias, seizures; watch for tetany and administer calcium and vitamin D as needed.

ADRENAL GLANDS

Functions

• Cortisol: Regulates blood sugar and metabolism; plays a role in the stress response.
• Aldosterone: Regulates sodium/potassium balance.
• Epinephrine/Norepinephrine: Required for fight-or-flight response.

Disorders of Adrenal Glands

• Cushing Syndrome-
    - Excess cortisol leading to various physical symptoms such as obesity and immunosuppression.
• Addison’s Disease: Adrenal insufficiency characterized by fatigue and hypotension, leading to an adrenal crisis if untreated.

Pheochromocytoma

• Rare tumors leading to excessive catecholamine release; diagnosed with imaging and treated with surgery.

Nursing Care

• Focus on monitoring electrolyte balance, blood pressure, and managing adrenal emergencies.