Yes, but you also have to take into account temporal effects. Its not only a spacial average, its a time average as well. Production and use might vary by time of day, depending on circadian or other timed factors. One of the reasons I did my biochem degree was because I got lost trying to figure out tissue and circadian factors in these things. I still get lost of course, this is complex stuff. For example, you could have some chemical produced at a particular level, or it could be produced at a low level except for a major spike, etc. Something like that happens with some hormones.