The severity of growth retardation in BC-<i>Tpst2^grt</i> mice is related to thyroid hypoplasia.

<p>A) Representative cross-sections of thyroid glands of BC-<i>Tpst2^grt</i> mice at 10 weeks of age. Upper: a male BC-<i>Tpst2^grt</i> mouse with severe growth retardation (body weight was 35.2% that of the littermate control; thyroid index = 16.3%). Lower: a male BC-<i>Tpst2^grt</i> mouse with mild growth retardation (body weight was 81.4% that of the littermate control; thyroid index = 47.4%). B) Plots of body weight and thyroid index of BC-<i>Tpst2^grt</i> at 10 weeks of age. Open triangles: BC-<i>Tpst2^grt</i> homozygous for <i>D2Mit255</i> (n = 8 and 6 for male and female, respectively), solid triangles: BC-<i>Tpst2^grt</i> heterozygous for <i>D2Mit255</i> (n = 6 and 6 for male and female, respectively), blue triangles: the average of DW-<i>Tpst2^grt</i> (n = 4 and 3 for male and female, respectively), red triangles: the average of 129-<i>Tpst2^grt</i> (n = 3 and 4 for male and female, respectively). C) Comparison of thyroid indices between genotypes at <i>D2Mit255</i> in BC-<i>Tpst2^grt</i> mice. a: homozygous, b: heterozygous for <i>D2Mit255</i>, respectively. Individual numbers are given in parentheses. Vertical lines indicate s.d. N.S.: not significant.