Abstract:
The dogmatic adherence to “what is good for the goose
is good for the gander” appears to pervade avian endocrinology
research when it comes to vertebrate evolution
of hormones and their physiological roles in birds.
There appears to be a general acceptance that specific hormones,
their cognate receptors, and their regulatory functions
identified in other vertebrates should be present and
serve the same function in birds. This has been largely the
case for leptin (LEP) originally identified in mammals (1–
5), which has been vigorously sought for more than a
decade in birds (6 –10), and also more recently for kisspeptin
(11, 12). But should we expect to find the same
hormones and functions in birds as occurs in other vertebrates?
In order for early reptilian bird ancestors to take to
the air, phenomenal evolutionary changes in their physiology
were required and presumably drove changes in the
use of existing hormones and cognate receptors, their
modification, or their abandonment. Yet many scientists
take the view that major physiological systems present in
tetrapods and fish should be present in birds and serve the
same function and use of the same hormone/receptor
regulators.
