The Mode of Action of Hormones

Higher organisms having anatomically and functionally differentiated organ systems must be able to coordinate biochemical processes within and between the various organs or cells, even under rapidly changing environmental conditions. Hormones play an important part in the regulation processes: they promote numerous metabolic reactions and differentiation processes, and show considerable differences in the speed with which they act. Some hormones act almost instantaneously by stimulating adenyl cyclase and thus initiating the production of adenosine 3′,5′‐monophosphate (cyclic AMP), which passes on the hormone message (“second messenger”) to the intracellular metabolism by modifying enzyme activities. Delayed‐action hormones, mainly morphogenetic hormones, act primarily on the cell nucleus where they induce the synthesis of certain enzymes by activation of genes.