Effect of Thyroid Hormone and Epidermal Growth Factor on Tactile Hair Development and Craniofacial Morphogenesis in Postnatal Rats

This study investigated the effects of triiodothyronine (T3) and epidermal growth factor (EGF) on the development of lateral tactile hair and craniofacial features in neonatal rats. Using 36 six-day-old Sprague-Dawley rats, researchers found that T3 and EGF significantly altered the angular displacement of lateral hairs compared to controls, with T3 reducing and EGF increasing the angle. Both hormones accelerated incisor eruption, with T3 having a greater effect, while EGF was more effective in accelerating palpebral morphogenesis. EGF delayed external ear development, whereas T3 accelerated it. Both hormones caused similar levels of somatic growth retardation. The study highlighted distinct and overlapping roles of T3 and EGF in craniofacial development.