The hormone most closely linked to breast pain is estrogen , especially when its level rises relative to progesterone in the menstrual cycle.

Key hormones involved

  • Estrogen : Rising estrogen before a period can make milk ducts and glands swell and trap fluid, leading to breast fullness and soreness.
  • Progesterone : Imbalances where there is relatively less progesterone than estrogen in the second half of the cycle are associated with cyclical breast pain.
  • Prolactin : Abnormal levels of prolactin, the hormone that helps with milk production, may also play a role in some cases of mastalgia.

When breast pain is hormonal

Hormone‑related (cyclical) breast pain often:

  • Follows the menstrual cycle and worsens before a period.
  • Feels like heaviness, aching, or tenderness in both breasts, sometimes with lumpiness or swelling.

If breast pain is severe, one‑sided, new, or comes with a lump, skin changes, or nipple discharge, a clinician should evaluate it promptly to rule out other causes.

TL;DR: Estrogen surges (often with relatively low progesterone) are the main hormonal drivers of breast pain, and prolactin can sometimes contribute as well.

Information gathered from public forums or data available on the internet and portrayed here.