I recently started eating large quantities of tofu because I heard it's a good source of lean protein, however, are there any negative side effects my new eating habits?

How much is a large quantity?

In general Tofu is a good food. In very large amounts, it's possible it could have a slight effect on your thyroid, and one small scale study found it tended to lower testosterone in men. But there is plenty of evidence that eaten in the right amounts, it's a useful addition to the diet.