Constant Splitting of Nail

Has anyone experienced this? On my thumb nail I have a line that goes the entire length of my nail. Eventually my nail will get to a good length and then it will split on the line and my nail will tear away from the skin. I've had this for years. Does this mean I'm deficient in something??? I don't know how to fix this but I'm really sick of my thumb nail being shorter than the rest so it doesn't tear off.