Vasoactive intestinal peptide stimulation of human thyroid cell function.

Neurons containing vasoactive intestinal peptide (VIP) have been found to reach thyroid follicular cells in man and other mammals. Human thyroid cells in culture were exposed to different concentrations of VIP and TSH, and thyroid cell activation was assessed by measurements of cAMP accumulation. VIP exerted a dose-dependent activation, and this thyroid-stimulating effect was more rapid and short-acting than that of TSH. At low concentrations of the two agents, their effects were additive, but they seemed to initiate their effects via different receptors, since polyphloretin phosphate inhibited the effect of TSH but not that of VIP. Moreover, antiadrenergic and anticholinergic agents did not influence thyroid activation by VIP. In addition to cAMP activation in cell cultures, VIP stimulated T4 release from human thyroid slices. It is possible that, in addition to sympathetic-adrenergic and parasympathetic-cholinergic nerves, VIPergic nerves may participate in the autonomic nervous control of thyroid function.