However, it seems unlikely that PCB effects on dendritic growth were due to hypothyroxinemia, because a) neonatal hypothyroidism decreases basal dendritic growth (Ruiz-Marcos et al. 1994; Uylings et al. 1994), whereas developmental PCB exposure significantly enhanced basal dendritic growth; and b) PCB effects on dendritic growth were recapitulated in cultured neocortical neurons removed from systemic thyroid hormone influence. Here, TG is linked to hypothyroidism.