Epidermal growth factor modulates thyroid growth and function in culture.

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.