MHT Micronized progesterone vs MPA & the Breast

This is a requested follow up to our most recent episode. Menopausal hormone therapy (HT) prescribing practices have evolved over the last few decades guided by the changing understanding of the treatment’s risks and benefits. We know that dose, route of administration, and choice of agent (estradiol versus a more synthetic option, and micronized progesterone over other progestins.) alter the risk benefit ratio. Compared to natural progesterone, synthetic progestins have 10-100- fold greater activity. Synthetic MPA is vasoconstrictive while natural progesterone and drospirenone cause vasodilation and lower blood pressure. Micronized progesterone is bioidentical to the hormone made endogenously and has efficient oral absorption. Progestogens come in oral and transdermal forms, and it can also be given vaginally. Is there data that micronized progesterone is safer for the breast for a menopausal hormone therapy? This podcast topic recommendation comes from one of our podcast family members. Listen for details. 1. Gompel A. Micronized progesterone and its impact on the endometrium and breast vs. progestogens. Climacteric. 2012 Apr;15 Suppl 1:18-25. doi: 10.3109/13697137.2012.669584. PMID: 22432812.2. Stute P, Wildt L, Neulen J. 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. PMID: 29384406.3. Eden J. The endometrial and breast safety of menopausal hormone therapy containing micronised progesterone: A short review. Aust N Z J Obstet Gynaecol. 2017 Feb;57(1):12-15. doi: 10.1111/ajo.12583. PMID: 28251642.4. Asi N, Mohammed K, Haydour Q, Gionfriddo MR, Vargas OL, Prokop LJ, Faubion SS, Murad MH. Progesterone vs. synthetic progestins and the risk of breast cancer: a systematic review and meta-analysis. Syst Rev. 2016 Jul 26;5(1):121. doi: 10.1186/s13643-016-0294-5. PMID: 27456847; PMCID: PMC4960754.5.AHA J Circulation: Rethinking Menopausal Hormone Therapy: For Whom, What, When, and How Long? 2023