The impact of micronized progesterone on breast cancer risk: a systematic review

Climacteric. 2018 Apr;21(2):111-122. doi: 10.1080/13697137.2017.1421925. Epub 2018 Jan 31.


Postmenopausal women with an intact uterus using estrogen therapy should receive a progestogen for endometrial protection. The debate on bioidentical hormones including micronized progesterone has increased in recent years. Based on a systematic literature review on the impact of menopausal hormone therapy (MHT) containing micronized progesterone on the mammary gland, an international expert panel's recommendations are as follows: (1) estrogens combined with oral (approved) or vaginal (off-label use) micronized progesterone do not increase breast cancer risk for up to 5 years of treatment duration; (2) there is limited evidence that estrogens combined with oral micronized progesterone applied for more than 5 years are associated with an increased breast cancer risk; and (3) counseling on combined MHT should cover breast cancer risk - regardless of the progestogen chosen. Yet, women should also be counseled on other modifiable and non-modifiable breast cancer risk factors in order to balance the impact of combined MHT on the breast.

Keywords: Micronized progesterone; breast biopsy; breast cancer risk; breast density; combined estrogen–progestogen therapy; hormone therapy; menopause.

Publication types

  • Systematic Review

MeSH terms

  • Breast / drug effects*
  • Breast Neoplasms / chemically induced
  • Endometrium / drug effects*
  • Estrogen Replacement Therapy* / adverse effects
  • Female
  • Humans
  • Menopause
  • Progesterone / administration & dosage*
  • Progesterone / adverse effects
  • Progestins / administration & dosage*
  • Progestins / adverse effects
  • Randomized Controlled Trials as Topic
  • Risk Assessment


  • Progestins
  • Progesterone