Thyroid and growth: thyroid hormones and development of the nervous system.

Growth and differentiation of nervous system are closely influenced by the presence of iodine and thyroid hormones during the first stages of development. The deficiency of thyroid hormones causes alterations of the maturation of the upper nervous cells (pyramidal cortical, Purkinje's cells) and of the glial cells with cell hypoplasia and reduction of dendritic branching, of synaptic spines and interneuronal connections. Experimental studies in hypothyroid rats evidenced impairments in the content and organization of intra-cytoplasmic microtubulin, in the biochemical maturation in synaptosomes and in the maturation of the nuclear and cytoplasmic receptors for T3.