HI: Can You Tell Me Why The Thyroid Nodule That

HI: Can you tell me why the thyroid nodule that I have owned for the past 16 years has suddenly started to grow slightly. I had a new biopsy and it is benign! And it doesn't affect my blood work, but I know it effected my metabolism. I can't find an answer to why this grows and remains benign? Can you tell me? Thanks, Gail