Endocrine relationships between rank - related behavior and antler growth in deer

In this review, we analyze endocrine aspects of the relationships between antlerogenesis and rank-related behavior. The explanation of these relationships has been based on the presumption that the antler growth is regulated by hormones modulated by agonistic behavior. Originally, we assumed that these relationships are primarily testosterone dependent. In the eighties, it was reported that the insulin-like growth factor 1 (IGF-1) is the antler-stimulating hormone. This hypothesis was supposed to replace an earlier theory that the antler-stimulating hormones are either androgens or their derivatives. Here, we present historical and recent views on these issues. In particular, we analyze the arguments in favor and against the role of testosterone and IGF-1 in antler growth and present a comparison of the results obtained across some deer species. In this context, we review and discuss experiments with castration of various deer species and analyze data from papers dealing with in vivo studies. We conclude that testosterone and not IGF-1 is the main antler stimulating and regulating hormone, and that concentrations of testosterone may be modified by social behavior.