GROWTH CURVE OF RAT THYROID UNDER A GOITROGENIC STIMULUS

The goitrogenic effect of methylthiouracil was studied in the male Wistar rat. A triphasic growth curve for thyroid weight consisting of a lag phase of 2 days, an exponential phase of 10 days followed by a plateau phase is described. As the follicular cell concentration remains constant throughout the three phases of the growth curve, the total thyroid follicular cell population undergoes an identical cell volume throughout the growth cycle suggest that, contrary to common supposition, cell hypertrophy does not precede hyperplasia in the goitrogenic response but is concomitant with it. The demonstration that under a goitrogenic stimulus the thyroid follicular cells reproduce exponentially provides a model for quantitative studies of agents affecting cell division in vivo. © 1969, The British Empire Cancer Campaign for Research. All rights reserved.