Why do organs end up a certain size? For example, two individuals of the same height and weight can have livers that vary widely in size.

It probably has to do with different types of growth hormone secretion during developing years and eventually tissues stop responding to these signals, but through what mechanism does the body know when to stop growing certain organs? Why doesn't the liver, for example, not just grow forever? What mechanism tells the body "yep, this organ is fully developed, make it stop growing"?

I've not found an answer to this question, is the answer actually known?