What defines hyperplasia?

Hyperplasia is characterized by an increase in the number of cells in a tissue or organ. This condition typically occurs in response to a stimulus, such as hormonal changes or increased demand on that particular tissue. For instance, hormonal hyperplasia can occur in the endometrium during the menstrual cycle, where an increase in estrogen leads to an expansion of the endometrial lining due to more cells being produced.

The correct answer appropriately identifies the essence of hyperplasia, distinguishing it from other cellular processes. For example, an increase in the size of existing cells is termed hypertrophy, while a decrease in cell size indicates atrophy. Additionally, a change from one type of cell to another is known as metaplasia. Therefore, selecting the option that defines hyperplasia as an increase in the number of cells directly captures the fundamental aspect of the process.