Is growth controlled by a hierarchical system?

A functional view of growth inevitably leads one to consider how it is controlled. There is much information on control mechanisms that regulate growth at different levels of organization within an organism. Some evidence is presented to establish that different types of control exist. However, our interest is in how the operation of these different control mechanisms might be co-ordinated, as it is clear that the can not operate autonomously. We consider a hierarchical arrangement of control systems, some of the implications for understanding normal growth processes, how it might have evolved and an interpretation of system failure.