Alterations in hair shaft morphology in the cretin rat

Hair samples were obtained from rats rendered hypothyroid in utero, when these animals reached 35 days of post-gestational age. The hairs were examined by scanning electron microscopy at a point on the shaft 340 mu from the bulb. All hairs, in the anagen phase, when compared, indicated that cretin rats had thinner hair shafts, more closely spaced cuticle cells, and more cuticle cells per unit of hair shaft. The surfaces of hairs from cretin rats were coronal, acuminated, and had dentate margins. It is therefore apparent that congenital hypothyroidism in rats affects the density, thickness, and surface characteristics of the hair.