MKI67 and goiter: Accompanying the increase in hematoxylin-stained nuclei (Figure 4A) and larger goiters in ChEL-KI animals (Figure 3B), thyroid cell proliferation by Ki67 immunostaining was increased in ChEL-KI mice compared to WT and cog/cog animals (Figure 4B,C, one-way ANOVA, p < 0.0001 and p < 0.0001, respectively).