I'm curious as to what the correlation (if any) between introverted personalities and public speaking? For my part, I'm a pretty big introvert. But I worked hard to develop my public speaking skills (toastmasters) and such. Now people don't believe me when I tell them I'm introverted. It should be noted that I never felt fear of public speaking, it was just something I wasn't particularly good at.
Great question. And congratulations on going to Toastmasters. That's a great place to (1) build speaking skills as you did in your case, and (2) desensitize your nervous system if you have anxiety.
Note that for those with a public speaking phobia, you may want to try SpeakMeister.com (if Toastmasters is too big of a step). The program is focused on making sure that you're practicing the right way so you can really overcome the anxiety.
Using the Myers-Briggs definition, being an introvert means that you tend to "re-charge your batteries" by being alone rather than with people (being with people too much depletes your energy). Extroverts tend to recharge their batteries and get energy mostly by being with people. Introversion is different from being shy (shy = being reserved or having or showing nervousness or timidity in the company of other people).
So with this definition, there is no correlation between introversion and public speaking anxiety. In fact, there's an article I read recently about President Obama possibly being an introvert. There are lots of introverts who are top public speakers.