Dr. Podolin's Endocrine Exam Essay # 3

Discuss how the following would affect TSH levels and thyroid hormone production:
    a)  Iodine deficiency
    b)  Thyroid-stimulating immunoglobulin
    c)  Hypothyroidism due to autoimmune destruction of the thyroid gland (Hashimoto's thyroiditis)

A.  Iodide deficiency

• Iodide (I) needed to make the building blocks for T₃ and T₄  

  • 1 I added to tyrosine to make MIT

  • 2 I's added to tyrosine to make DIT

    • 1 MIT and 1 DIT joined to make T₃

    • 2 DIT's joined to make T₄

• If there is no I than MIT and DIT cannot be made so there is a DECREASE in T₃ and T₄ production.

  • Since there is a lower than needed level of T₃ and T₄ , the anterior pituitary releases MORE TSH in an attempt to make T₃ and T₄ 

    • This causes HIGH TSH levels

B.  Thyroid Stimulating Immunoglobin (TSI)

• TSI is an immunoglobin antibody that binds to the same receptor sites that bind TSH

  • TSI when bound to the thyroid cells induces a continual production of T₃ and T₄ 

    • HIGH T₃ and T₄ production levels

      • Hyperthyroidism - Graves Disease

  • TSI lasts nearly 12 times as long as TSH

• Because of larger than needed T₃ and T₄ levels,

  • The body inhibits the release of TSH

    • A LOW TSH level

C.  Hypothyroidism due to autoimmune destruction of thyroid gland (Hashimoto's Thyroiditis)

• Usually initially caused by the inflammation of thyroid gland

  • Causes deterioration and fibrosis of thyroid

    • Causing diminished or absent thyroid production

      • LOW T₃ and T₄ production levels

• Due to LOW T₃ and T₄ levels the anterior pituitary releases more TSH to try and stimulate T₃ and T₄ production

  • HIGH TSH levels

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