Effects of thyroxine on cell proliferation in human multinodular goiter: A study on growth of thyroid tissue transplanted to nude mice

Abstract

Abstract To analyze the inhibitory effect of thyroxine (T4) on thyroid growth, freshly obtained biopsies of human nontoxic multinodular goiter tissue from 9 patients were transplanted to nude mice. After the implantation period, thyroid growth was stimulated by either hemithyroidectomy (HT) or by administration of the goitrogen propylthiouracil (PTU), with or without simultaneous administration of T4. During the latter period, 3 H‐thymidine was continuously administered by osmotic minipumps to label replicating cells. After processing of the tissue for autoradiography, the fraction of labeled cells (LI) was calculated. Following HT, the fraction of labeled cells in nontoxic multinodular goiter tissue was 4.8%. T4 significantly reduced the LI to 1.0%. The goitrogen induced transplant growth, the LI varying between 28% and 61% in the different specimens. Administration of T4 resulted in lower LI in all transplants: in 5 specimens the LI was similar to control transplants. In transplants from 3 goiter specimens, however, significantly higher LI were found . The present results show that administration of T4 significantly inhibits growth of human thyroid tissue. The effect seems, however, to vary in different specimens of nontoxic goiter, indicating a varying degree of autonomous replicating activity .