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Why do milk-producing structures in the breast decrease after lactation ends?

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atrophy One example of atrophy is the progressive loss of bone that occurs in osteoporosis (normal bone shown on left; osteoporotic bone shown on right).

The decrease in size of milk-producing structures in the breast after lactation ends is a normal physiological process known as atrophy.

Atrophy refers to the reduction in the size or number of cells within an organ or tissue that was previously of a normal size for the individual's circumstances. In the context of the female reproductive system, this is a natural, cyclic change. Just as the uterus undergoes rapid atrophy following childbirth, the acinar structures (the milk-producing glands) of the breast diminish in size once the stimulus for lactation—which is maintained by hormonal patterns and the act of suckling—is withdrawn. This process allows the tissue to return to a resting state after the functional demands of milk production have ceased.12