“…Since at this time, fetal thyroid function in the mouse is still inactive, and these early signals may reflect maternal T 4 or T 3 activity. Early T 3 signaling was observed in the brain (i.e., diencephalic primordia, medulla oblongata) and sense organs primordia (otic vescicle, olfactory epithelium, retina), whereas at late stages (E15.5-E17.5) beta-gal expression was localized in other primordia (i.e., in the bones, follicular nerves of the vibrissae, as well as in the small intestine primordia, but also in the medulla oblongata) (468).…”