Epidermal Growth Factor Modulates Thyroid Growth and Function in Culture*

Abstract

The effect of epidermal growth factor (EGF) on the growth and function of porcine thyroid follicle suspension cultures was examined. When incubated with EGF (0.01-10 ng/ml), the incorporation of [3H]thymidine was markedly stimulated, with the half-maximal effect occurring at about 0.5 ng/ml. Through 6-day experiments, [3H]thymidine incorporation increased almost linearly after an initial lag phase of 1 day. Autoradiographical analysis showed that more than 50% of the nuclei were labeled after 4 days of incubation with EGF (10 ng/ml) compared to control values of 3-7% labeled nuclei. EGF was essentially as effective in serum-free medium as in medium containing 1% fetal calf serum. EGF added at the same concentrations that stimulated incorporation of [3H]thymidine was found to reduce iodide metabolism of the follicles within 30 min of addition; both TSH-stimulated efflux and organification of [125I]iodide were suppressed by the addition of EGF. Since EGF is a physiologically occurring substance, the data suggest that EGF might be a modulator of thyroid growth and function in vivo.