14.Endocrine PT1_study_guide

Endocrine System Overview

• Endocrine System: Consists of glands that secrete hormones directly into the bloodstream to regulate various body functions.

I. Functions of Hormones

• Hormones: Chemical messengers produced by endocrine organs.

  • Function: Modulate activity of target cells.

  • Mechanism: Bind to receptor sites on or in target cells, triggering an intracellular response.

  • Metabolism: Inactivated at receptor sites or by the liver.

II. Major Components of the Endocrine System

• Pituitary Gland (Master Gland): Produces hormones that control many other endocrine glands.

  • Anterior Pituitary:

    • Growth Hormone (GH): Essential for growth; regulates metabolism (protein synthesis, fat mobilization).

    • Prolactin: Stimulates milk production.

    • Melanocyte-Stimulating Hormone (MSH): Increases melanin production.

    • Tropic Hormones:

      • Adrenocorticotropic Hormone (ACTH): Stimulates secretion of cortisol and androgens from the adrenal cortex.

      • Thyroid-Stimulating Hormone (TSH): Promotes secretion of thyroid hormone and growth of the thyroid gland.

      • Follicle-Stimulating Hormone (FSH): Promotes follicle maturation and estrogen production in women; stimulates spermatogenesis in men.

      • Luteinizing Hormone (LH): Induces ovulation and progesterone production in women; stimulates testosterone production in men.

  • Posterior Pituitary:

    • Oxytocin: Triggers uterine contractions and milk letdown.

    • Antidiuretic Hormone (ADH): Promotes water retention in kidneys.

III. Hypothalamus

• Part of the CNS; regulates pituitary gland function by producing releasing/inhibiting hormones.

  • Releasing/Inhibiting Hormones:

    • Gonadotropin-Releasing Hormone (GnRH): Stimulates FSH and LH release.

    • Growth Hormone-Releasing Hormone (GHRH): Stimulates GH release.

    • Somatostatin: Inhibits GH release.

    • Thyrotropin-Releasing Hormone (TRH): Stimulates TSH release.

    • Corticotropin-Releasing Hormone (CRH): Stimulates ACTH release.

IV. Other Key Endocrine Organs

• Thymus: Produces thymosin, affecting immune system and lymphocyte development.

• Ovaries/Testes: Produce sex hormones (estrogen, progesterone, androgens).

• Thyroid: Produces T3, T4, and thyrocalcitonin for metabolism and calcium regulation.

• Parathyroid Glands: Secrete parathyroid hormone (PTH) for calcium regulation.

• Adrenal Glands:

  • Cortex: Produces mineralocorticoids, glucocorticoids, and sex hormones.

  • Medulla: Produces catecholamines (epinephrine, norepinephrine).

• Pancreas:

  • Exocrine function: Secretes digestive enzymes.

  • Endocrine function (Islets of Langerhans):

    • Alpha Cells: Secrete glucagon.

    • Beta Cells: Secrete insulin.

V. Control of Hormone Levels

• Feedback Mechanisms: Adjust hormone secretion based on the level of specific substances in the body.

  • Negative Feedback: Decreased hormone levels lead to increased hormone production, and vice versa.

• Cyclical Patterns: Some hormones exhibit patterns of release based on time or physiological cycles.

VI. Common Endocrine Problems

• Hypofunction vs. Hyperfunction:

  • Hypofunction Causes:

    • Congenital defects.

    • Gland damage or atrophy.

    • Aging effects.

    • Hormonal inactivity or destruction by antibodies.

  • Hyperfunction Causes:

    • Excessive stimulation by autoantibodies.

    • Hormone-producing tumors.

    • Ectopic hormone production (e.g., from lung tumors).

• Primary vs. Secondary Problems:

  • Primary: Originates from the gland producing the hormone.

  • Secondary: Normal gland function altered by regulatory issues (e.g., hypothalamic or pituitary issues).

VII. Pathological Changes and Nursing Considerations

• Thyroid Hormones:

  • Actions: Increase metabolic rate, facilitate growth, and thermal regulation.

  • Pathological Changes:

    • Hyperthyroidism: Increased hormone levels due to autoimmune disorders or tumors.

    • Hypothyroidism: Decreased hormone levels due to congenital defects or autoimmune diseases.

  • Assessment Findings: Symptoms associated with conditions like Graves' disease and Hashimoto thyroiditis.

• Adrenal Cortex Hormones:

  • Functions: Regulate sodium, water balance, stress response, and immune function.

  • Pathological Changes: Examples include Addison's disease (hypofunction) and Cushing's syndrome (hyperfunction).

  • Assessment Findings: Specific symptoms based on hormone imbalances.

• Adrenal Medulla Hormones (Catecholamines):

  • Dysfunction: Increased levels due to tumors lead to symptoms of pheochromocytoma.