Hypertrophy refers specifically to an increase in the size of individual cells, not an increase in the number of cells (which is hyperplasia).

At its core, hypertrophy is a cellular response characterized by an increase in the volume of existing cells. This expansion typically involves the synthesis of additional intracellular proteins and organelles, leading to an overall enlargement of the tissue or organ. This is a critical distinction from hyperplasia, where the tissue grows due to an increase in the *number* of cells through cell division. While both lead to organ enlargement, their underlying cellular mechanisms and implications can be vastly different. For example, skeletal muscle typically undergoes hypertrophy in response to resistance training, as muscle cells (myocytes) increase in size by synthesizing more contractile proteins. In contrast, certain hormonal stimuli might cause hyperplasia in glandular tissues, leading to more cells producing hormones. However, some tissues can exhibit both hypertrophy and hyperplasia, especially in pathological conditions.