why do my boobs hurt before my period

Breast pain before a period, known as cyclic mastalgia, is very common and primarily caused by hormonal changes during the menstrual cycle. Specifically, fluctuations in estrogen and progesterone levels in the second half of the cycle (the luteal phase) lead to swelling of the breast ducts and milk glands, causing tenderness, swelling, and pain. Estrogen causes breast ducts to enlarge, and progesterone causes the milk glands to swell, which can make breasts feel sore or tender before the period starts. This pain usually goes away once the period begins and affects up to 70% of women. Other factors like increased prolactin levels and lymph node swelling may also contribute to the discomfort.