The World of HormonesMolecular and Physiological Insights

The field of the study of hormones, called endocrinology, originated with the discovery of insulin in the 1920s and the characterization of the steroid hormones in the 1930s. Recent additions to the list of over 150 molecules that serve as hormones include 9-cis-retinoic acid (derived from vitamin A), atrial natriuretic... read morehormone (secreted by the heart), nitric oxide (a gas) and leptin (secreted by fat cells).

Classically, a hormone is defined as a chemical messenger secreted by an endocrine gland and delivered through the circulatory stem to target cells that possess receptors specific for the hormone. Today, this definition of a hormone has been broadened beyond systemic messengers to include locally acting paracrine and autocrine messengers such as growth factors and interleukins or cytokines. For all these chemical messengers, occupancy of their cognate receptor leads to the initiation of signal transduction processes that result in generation of specific biological responses.

The study of the signal transduction processes that are activated by hormones is currently flourishing, so that there is a plethora of information with regard to defining the molecular identity of the specific signal transduction pathway(s) employed between occupancy of the receptor and the emergence of the final biological response(s). Finally, the ability to determine the three-dimensional structure of the hormones and their receptors via x-ray crystallography and NMR evaluation gives intimate insight into the specific nature of the molecular contacts that stabilize receptor interactions with their hormones or drug surrogates.

The science of molecular endocrinology is now in the position to provide molecular answers to important hormone-related medical problems and to provide structure/function-based hypotheses for the design of drug agonists and antagonists for specific diseases.