From what I've read, Stevia produces insulin.

I have been diagnosed with PCOS (poly-cystic-ovarian syndrome) in my opinion because mercury is mimicking the symptoms, but this condition is rooted in Insulin Resistance - which means the body is making too much insulin already. To reduce the amount of insulin made by the body, those with IR need to reduce the amount of insulin-making foods (hence need to reduce carbs). Thus I don't think Stevia would be good for those who have IR - or maybe even those with mercury toxicity if it causes IR.

I've also read concernes that Stevia is toxic, but as they gave the animals the equivalent of 600 times the amount a person would consume, the findings are extremely doubtful.