Endocrine System: Thyroid and Pituitary Gland Lecture

Jun 15, 2024

Thyroid Gland and Pituitary Gland

Pituitary Gland

  • Located in the brain, known as the "master gland"
  • Produces Thyroid Stimulating Hormone (TSH)

Thyroid Gland

  • Located in the neck, attached to the trachea
  • Produces thyroxine (T3 and T4)
  • Requires iodine from diet for thyroxine production
  • Structure contains a precursor called thyroglobulin

Hormones and Their Interaction

  • TSH: Produced by pituitary, stimulates thyroid to produce thyroxine
  • Thyroxine (T3 and T4): Contains iodine; T3 has 3 iodines, T4 has 4 iodines
  • Dietary Iodine: Crucial for thyroxine production, can come from seafood
  • Example: Radioactive iodine can be used to destroy thyroid tissue in cancer treatment

Negative Feedback Loop

  • Presence of thyroxine in blood regulates TSH production
    • High thyroxine → Low TSH production
    • Low thyroxine → High TSH production
  • Hypothyroidism: Diagnosed by elevated TSH
  • Hyperthyroidism: Diagnosed by low TSH
  • Aka a "negative feedback loop"

Functions of Thyroxine

  1. Increase ATP Production: Enhances oxygen and glucose consumption, increases cellular activity
  2. Cardiovascular Effects: Increases heart rate and blood pressure
  3. Blood Production: Stimulates red blood cell production in bone marrow
  4. Brain Activity: Enhances mood, energy, and clarity of thinking

Thyroid Dysfunctions

Hypothyroidism

  • Causes: Imbalances post-pregnancy, autoimmune diseases (e.g., Hashimoto's)
  • Symptoms:
    • Brain: Foggy thinking, depression, low energy
    • Heart: Low heart rate, low blood pressure
    • Red Blood Cells: Anemia, feeling cold, pallor, fatigue
    • Metabolism: Overweight, tiredness, low ATP production

Hyperthyroidism

  • Causes: Autoimmune diseases (e.g., Graves' disease), thyroid cancer
  • Symptoms:
    • Brain: Agitation, irritability
    • Heart: Rapid heart rate, high blood pressure, exophthalmos (eye protrusion)
    • Red Blood Cells: May cause polycythemia (though not typical term), feeling hot, flushed
    • Metabolism: Weight loss, restlessness

Diagnosis and Treatment

  • Diagnosis: TSH Levels
    • Elevated TSH: Typically indicates hypothyroidism
    • Low TSH: Typically indicates hyperthyroidism
  • Treatment: Radioactive Iodine
    • Used to kill thyroid cells in cancer or severe hyperthyroidism cases