Effects of hypothyroidism on postnatal development in the peripheral vestibular system.

The morphogenetic effects of congenital hypothyroidism on the development of rat vestibular receptor cells and ganglia were investigated by transmission electron microscopy. Vestibular ganglia are especially immature and characterized by an absence of a myelin sheath around the perikarya. The type I hair cells have a delayed development in their innervation. The last cells to differentiate and the last synaptic contacts to develop are the most affected. The most remarkable result of hypothyroidism is the persistent immaturity of the synaptic contacts.