It is believed that thyroid hormones evolved in the Urbilaterian well before the development of the thyroid itself and molluscs, echinoderms, cephalochordates and ascidians all use such hormones. Cnidarians also respond to Thyroid hormone despite being parahoxozoans rather than bilaterians.
Insects use hormones similar to thyroid hormone using iodine.
Phosphorylated tyrosines created with tyrosine kinases are fundamental signalling molecules in all animals and in choanoflagellates.