A 28-year-old pregnant woman from a coastal village is found to have a goiter. Her dietary iodine intake is adequate. Further evaluation reveals selenium deficiency. How does selenium deficiency worsen iodine deficiency disorders?
- A Selenium is required for thyroglobulin synthesis
- B Selenium is a component of iodothyronine deiodinase (type I deiodinase) needed for T4 to T3 conversion ✓
- C Selenium deficiency increases thyroid-binding globulin levels, reducing free T4
- D Selenium acts as a cofactor for the sodium-iodide symporter in thyroid follicular cells
Correct answer: B. Selenium is a component of iodothyronine deiodinase (type I deiodinase) needed for T4 to T3 conversion
Explanation
Selenium is an essential component of selenoproteins, including the family of iodothyronine deiodinase enzymes. Type I deiodinase (predominant in thyroid and liver) converts T4 to the biologically active T3. Selenium deficiency impairs this conversion, reducing T3 levels and increasing TSH, which stimulates thyroid hypertrophy and exacerbates iodine deficiency disorders. Selenium is also part of glutathione peroxidase, which protects the thyroid from H₂O₂ generated during iodination.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.