During the metabolism of iodine in thyroid synthesis, Wolff-Chaikoff effect is seen due to:

Iodine metabolism within the thyroid can be regulated independently of TSH. This mechanism is impoant when plasma iodide levels are elevated (15-20-fold above normal) because this elevation inhibits the organic binding of iodine within the thyroid. This autoregulatory phenomenon consisting of inhibition of the organification of iodine by elevated circulating levels of iodide is known as the Wolff-Chaikoff effect. This effect lasts for a few days and is followed by the so-called escape phenomenon, at which point the organification of intra-thyroidal iodine resumes and the normal synthesis of T4 and T3 returns. Ref: Molina P.E. (2013). Chapter 4. Thyroid Gland. In P.E. Molina (Ed), Endocrine Physiology, 4e.