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Thyroid hormones and Antibodies

  1. Thyrotropin Releasing Hormone (TRH):
  •    Secreted by the hypothalamus.
  •    Stimulates the anterior pituitary to release TSH.

 

  1. Thyroid Stimulating Hormone (TSH):
  •    Acts on follicular cells in the thyroid.
  •  Prompts these cells to produce and release thyroid hormones and thyroglobulin.

 

  1. Thyroglobulin (Tg):
  •    A glycoprotein made by thyroid follicular cells.
  •    Found in the lumen of thyroid follicles.
  •  After total thyroidectomy or radioactive iodine treatment, Tg levels should be zero; presence indicates disease recurrence.

 

  1. Calcitonin:
  •    Produced by parafollicular C-cells of the thyroid.
  •   Lowers the number and activity of osteoclasts, reducing bone resorption.
  •    High levels are seen in medullary carcinoma.

 

  1. TSH-Receptor Antibodies:
  •   Found in Graves’ disease.
  •  These antibodies bind to TSH receptors on follicular cells, stimulating them to produce T4 and T3 hormones, leading to hyperthyroidism.

 

  1. Thyroglobulin Antibodies:
  •    Develop in autoimmune thyroid disorders like Hashimoto’s disease, causing hypothyroidism.
  •    Usually associated with thyroid peroxidase (TPO) antibodies.

 

  1. Thyroid Peroxidase (TPO):

   – An enzyme responsible for:

  •      Converting iodide to iodine.
  •      Iodinating tyrosine to monoiodotyrosine.
  •  Coupling monoiodotyrosine with di-iodotyrosines to form T3.
  •      Coupling di-iodotyrosines to form T4.

 

  1. Antimicrosomal Antibodies:
  •    Also known as antiperoxidase antibodies.
  •    Found in autoimmune thyroid disorders.

 

  1. Antiperoxidase (TPO) Antibodies:
  •    Present in nearly all cases of Hashimoto’s disease and 80% of Graves’ disease cases.

 

  1. Propylthiouracil and Methimazole:
  •     These medications impair the organification of iodine, reducing T4 and T3 levels.
  •     Used to treat hyperthyroidism.
  •     Propylthiouracil is preferred during pregnancy as it does not cross the placental barrier.
  1. Excess Iodine:
  •     Inhibits the release of thyroid hormones (Wolff–Chaikoff effect), causing a drop in T4 and T3 levels.
  •     Lugol’s iodine or potassium iodine is used to prepare hyperthyroid patients for surgery.

———- End of the chapter ———–

Learning resources.

  • Scott-Brown. Textbook of Otorhinolaryngology Head and Neck Surgery.
  • Harrison’s principles of internal medicine.
  • David J. Terris. William S. Duke. Textbook of Thyroid and Parathyroid Diseases Medical and Surgical Management.
  • Stell and Maran’s. Textbook of Head and Neck Surgery and Oncology.
  • Hans Behrbohm. Textbook of Ear, Nose, and Throat Diseases With Head and Neck Surgery.
  • P L Dhingra. Textbook of Diseases of Ear, Nose and Throat.
    •  

    Author:

Dr. Rahul Bagla ENT Textbook

Dr. Rahul Bagla
MBBS (MAMC, Delhi) MS ENT (UCMS, Delhi)
Fellow Rhinoplasty & Facial Plastic Surgery.
Designation: Faculty, Associate Professor
Government Institute of Medical Sciences,
Greater Noida, India
Mail: msrahulbagla@gmail.com

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