Endocrinology and Evolution

Molecular biology advances have assisted comparative endocrinology. Previously the characterization of hormones in ‘lower’ vertebrates relied upon biological assays and protein chemistry, whereas now genes are readily revealed in whole genome sequences, and specific antibodies and other reagents for sensitive assays can rapidly be developed, enabling revealing physiological experiments. Comparative endocrinology only became a special field in the last 50 years as endocrinologists concentrated on rodents as their preferred animal model. In the past many of the known hormones were originally identified in ‘lower’ vertebrates. Two paradigmatic examples of the value of comparative endocrinology will be highlighted. Calcium regulating factors, both hypercalcaemic and hypocalcaemic, will be discussed before thyroid hormones. Both groups of hormones are essential for human life during development and in adulthood, and pivotal insights have been gained from non-mammalian vertebrates.