The thyroid hormones (THs), thyroxine (T4) and triiodothyronine (T3) are products of the
thyroid gland in all vertebrates. Their role in early development and metamorphosis is well
established in mammals and amphibians, respectively, and recently several studies in fish
have highlighted the importance of THs during flatfish metamorphosis. THs are present in
high quantities in fish eggs and are presumably of maternal origin. During embryogenesis
the concentration of T4 and T3 in the eggs decrease until endogenous production starts …