Hyperplasia is an increase in the number of cells in an organ due to increased cell proliferation. There are two types of hyperplasia: physiological and pathological. Physiological hyperplasia occurs normally, such as the growth of breast tissue during puberty and pregnancy or the compensatory growth of liver cells after partial resection. Pathological hyperplasia is caused by excessive hormones or growth factors and can lead to conditions like endometrial hyperplasia or benign prostatic hyperplasia. The hyperplastic process remains controlled and will disappear if the initiating signals subside.