The psychology of nymphomania
::: It seems like you're trying to get to the root cause as either organic or functional? Maybe a bit of both. They jury will forever be out thus we have the stress-diathesis model for comfort. Here is some interesting discussion on the norm-referencing in assessment of manic behavior such as hypersexuality and the implications of various factors like gender. OOhh - this is a good one too actually- a very large study on the whole range of abnormal sexual activity. 

In working with individuals who are hypersexualized, i've found that it's learned, it's reactive attachment gone awry...co-occurring borderline meets cyclic dysthmia.... it's never just hormone or just addiction. I have not looked at extreme cases really, though...