Since there was a comment about wondering how the testosterone affected things:
I went on testosterone in November 2007 at a dose of 200mg per 2 weeks. My overall insulin needs increased in the following months, although gradually enough to keep up with them, by about 25%. In April 2008, I lowered the dose to 180 mg per 2 weeks because I wasn't liking the feeling of the dose; my doctor said it didn't matter.
In July 2008, blood tests revealed that my testosterone levels were well above the male range, and I dropped my dose from 180mg per two weeks, to 120 mg per two weeks. In the following weeks, my insulin needs fell dramatically. The Lantus needs dropped by more than half, and the Novolog needs decreased a little bit.
In January 2009, my testosterone levels appeared to be almost as elevated as before, and the dose was dropped to 80 mg per two weeks, and my insulin needs fell even further.
Since then, I've gone up and down on the testosterone. When I've gone off of it entirely at gallbladder times, I've seemed to need a little bit more insulin, but changing the dose within the range of 40-70 mg per two weeks doesn't seem to matter as far as my insulin needs go.
When my insulin needs change, the way my insulin needs have been higher in the past month, testosterone levels are something I wonder about as the culprit.
Among women, higher testosterone levels, as in diseases such as polycystic ovarian syndrome and adrenal hyperplasia, are associated strongly with insulin resistance (higher insulin needs).
Among men, testosterone levels in the upper normal range are associated with the most insulin sensitivity (lower insulin needs), and having testosterone in the bottom or below normal is strongly associated with type 2 diabetes. Having testosterone above the normal male range is also associated with insulin resistance.
My theory, then, is that there are two sweet spots in terms of testosterone levels that bodies like. Prior to taking testosterone, my levels were not in either the female nor the male normal ranges- my testosterone level was about twice the upper end of the female normal range, which still put it at less than a third the bottom of the male normal range. I assume that caused insulin resistance.
When I went on testosterone, I initially went from a testosterone level that was between the sweet spots, to one that was too far above the male range and therefore not much better as far as my health was concerned, but dropping the dose has landed me solidly in the upper end of the male range- an insulin sensitivity sweet spot.
But that's just a theory.