The thyroid produces mostly thyroxine (T4), which must convert to triiodothyronine (T3) โ the active hormone.
Polyunsaturated fatty (PUFAs) acids slow this conversion, possibly by:
1. Inhibiting 5โ-deiodinase, the enzyme that converts T4 โ T3
2. PUFAS also increasing oxidative stress in liver cells, which impairs normal metabolism
3. PUFAs and their oxidation products can bind to thyroid transport proteins or cell receptors, reducing how effectively T3 gets into cells.
4. Animal studies have shown that feeding high-PUFA diets can lower TSH output from the pituitary gland, slightly reducing thyroid stimulation.
