During puberty, the rise in the hormone estrogen in your body causes the pituitary gland to make more growth hormone. This causes you to grow at a much faster pace than you had been growing.
This growth process happens later for boys, which is why you may find yourself taller than the boys in your class for a while. Rarely, there is too little or no growth hormone being made. If this happens, girls and boys may not have their growth spurt. Again, this is uncommon. Consult a doctor incase of uncommon symptoms.