Impaired neurogenesis in the growth-retarded mouse is reversed by T ₃ treatment

Triiodothyronine (T₃) regulates neuronal development, and T ₃ deficiency impairs the formation of the central nervous system during childhood. Here, we used the hypothyroidal growth-retarded (grt) mouse to investigate whether the generation of new neurons is affected by T₃ deficiency. Cell proliferation in the hippocampus, as measured by 5-bromo-2′-deoxyuridine (BrdU) incorporation, was markedly decreased in the grt mouse while the number of BrdU-positive cells in T₃-treated grt mice was equivalent to that of wild type mice. The cellular differentiation rate did not differ among the experimental groups. These results suggest that T₃ plays an important role during neurogenesis.