Endocrine 2

Overview of Endocrine System and Thyroid Function

Endocrine Glands and Their Secretions

• Pituitary Gland:

  • Components: Adenohypophysis (Anterior Pituitary, endocrine tissue), Neurohypophysis (Posterior Pituitary, neural tissue)

  • Hormones: FSH, LH, IGF-1, oxytocin, vasopressin

• Thyroid Gland:

  • Anatomy: Approximately 15-20 grams, essential for normal function

  • Components: Colloid (contains thyroglobulin), T4 (Thyroxine), T3 (Triiodothyronine)

  • Iodine Role: Essential for hormone production; trapped by follicular cells for synthesis

Hormone Synthesis and Control of Activity

• Thyroid Hormone Synthesis:

  • Iodination of tyrosine residues forms MIT and DIT, leading to T3 and T4

• Control Mechanism:

  • TSH levels regulated by TRH; negative feedback from T4 and T3

• Posterior Pituitary Functions:

  • Hormone synthesis in supraoptic and paraventricular nuclei; processed and released near capillary blood vessels

Iodine Deficiency and Effects of Thyroid Hormones

• Consequences of Iodine Deficiency:

  • Decreased synthesis of T4 and T3 leads to goiter formation

• Physiological Effects of Thyroid Hormones:

  • Increase metabolic rate and cardiac output, modulate metabolism, stimulate growth, and impact brain development

Thyroid Dysfunction

• Hypothyroidism:

  • Low T4/T3 levels, symptoms include weight gain and lethargy

• Hyperthyroidism:

  • High T4/T3 levels, symptoms include weight loss and nervousness

• Types of Hypothyroidism:

  • Primary (Myxedema), Secondary (Inadequate TSH), Tertiary (Inadequate TRH), Infantile

• Types of Hyperthyroidism:

  • Primary (Graves' disease), Secondary (Pituitary tumors), Tertiary (Hypothalamic tumors)

• Treatment for Hyperthyroidism:

  • Surgical removal, radioactive iodine therapy, antithyroid medications

Endocrine Control of Calcium Homeostasis

• Importance of Calcium: Structural component of bones, involved in clotting and cell excitability; hormonal control via PTH, calcitonin, and vitamin D

• Key Hormones:

  • PTH: Increases blood calcium levels

  • Calcitonin: Decreases blood calcium levels

  • Vitamin D: Increases dietary absorption and renal regulation of calcium

Conclusion

This structured overview aligns the information on the endocrine system and thyroid function, focusing on key glands, their hormonal activities, and how they relate to calcium homeostasis and thyroid conditions.