Receptors for insulin and insulin-like molecules

An increasing body of evidence supports the regulation of hormone action by changes in receptor concentration and affinity. Down and up regulation of insulin and somatomedin receptors by changes in hormone concentration explains the alterations in receptor numbers in obesity or diabetes. However, the changes in receptor affinity that have been described have no known mechanism. In most cases, they occur in vivo, but changes can be produced in vitro by ketone bodies and calcium ions. Calcium ions have also been implicated in insulin action, thus strengthening this relationship. Evaluation of the control of receptor affinity must take into account the effects of metabolites such as glucose and minerals, as well as multiple other factors. The relationship between binding and the biological effect of insulin has to be resolved before the full understanding of insulin action can be reached. The controversial areas of insulin receptor research are becoming clearer, but much more information is required before these questions can be resolved.