Receptor secretion hypothesis for regulation of hormone action

It is well established that modulation of target cell responses to hormonal stimulation can occur through variation of the number of effective hormone receptors per cell. Recent experimental evidence suggests that an alternative or additional autoregulatory mechanism may operate via secretion by the cell of 'receptors' which can bind to, and thereby regulate, the concentration of free hormone in the extracellular space. We present here a brief general analysis of this 'receptor-secretion' model, together with an example which shows that it can readily account for the phenomenon of self-limiting growth seen in many tissues in response to sustained hormonal stimulation. The biological significance of the model is discussed, and the close analogy with B-lymphocyte regulation pointed out. Finally, two important implications are considered, for the pathogenesis of nodular hyperplasia and tumours in hormonally-controlled tissues.