What themes unify comparative endocrinology?
Two types of themes that receive considerable attention in comparative endocrinology are: 1. Evolutionary patterns – For example, ancestral organisms may have a single hormone that performs a series of functions while more recently evolved organisms may have several related hormones each of which performs a single one of these functions. 2. Chemical structure and function of hormones in different organisms – In some cases, hormones are identical chemically in all vertebrates (e.g. thyroid hormones) and may have similar functions (e.g. thyroid hormones trigger developmental events in all vertebrates). In other cases, the same hormone may have different effects in different organisms (e.g. thyroid hormones increase metabolism in birds and mammals but do not do so in other vertebrates). In yet other cases the chemical structure of a hormone may differ even in closely related species, a common situation for complex protein hormones. How diverse is the field of comparative endocrinology? Th
