Do hormones cause cancer? The fear traces to one day in July 2002, when the Women's Health Initiative stopped one arm early: Premarin, a horse estrogen, with MPA, a copycat progestin. Neither arm of that trial gave estradiol or progesterone, and the same program's trial of Premarin alone ended up with fewer breast cancers and fewer breast cancer deaths than placebo.Five questions that take apart any cancer headline. Where the fear came from. Estradiol and the breast, trial by trial. Why the breast signal follows the copycat progestin, not progesterone. Testosterone as the breast's brake. And the drivers you can actually act on: body fat, insulin, alcohol and light at night.Part two, Wednesday: family history and BRCA, the breast cancer survivor, tamoxifen and the aromatase inhibitors, the prostate, every other cancer, and who benefits from keeping patients off hormones.All research, opinions and clinical judgment are my own. This is education, not individualized medical advice.CHAPTERS00:00 Cold open: do hormones cause cancer?04:28 Five questions for any cancer headline11:59 Where the fear came from24:57 Estradiol and the breast33:10 Progesterone vs progestins46:12 Testosterone, the brake51:04 If not hormones, the real drivers56:44 Close: part oneSOURCESAdair & Herrmann 1946, Ann Surg, 123, 1023-35Agrawal et al. 2024, J Sex Med, 21, 414-419Anderson et al. 2012, Lancet Oncol, 13, 476-86Brinton & Felix 2014, J Steroid Biochem Mol Biol, 142, 83-9Chlebowski et al. 2010, JAMA, 304, 1684-92Chlebowski et al. 2020, JAMA, 324, 369-380Chlebowski et al. 2024, Breast Cancer Res Treat, 206, 177-184Coelingh Bennink et al. 2017, Maturitas, 95, 11-23Collaborative Group on Hormonal Factors in Breast Cancer 2019, Lancet, 394, 1159-1168Cordina-Duverger et al. 2013, PLoS One, 8, e78016Crandall et al. 2018, Menopause, 25, 11-20de Lignières et al. 2002, Climacteric, 5, 332-40Dimitrakakis et al. 2004, Menopause, 11, 531-5Donovitz & Cotten 2021, Eur J Breast Health, 17, 150-156Ellis et al. 2009, JAMA, 302, 774-80Fels 1944, J Clin Endocrinol, 4, 121-125Fournier et al. 2008, Breast Cancer Res Treat, 107, 103-11Fournier et al. 2014, Breast Cancer Res Treat, 145, 535-43 (via Stute et al. 2018)Fournier et al. 2014, Am J Epidemiol, 180, 508-17Frandsen et al. 2024, Breast Cancer Res Treat, 208, 535-542Glaser & Dimitrakakis 2013, Maturitas, 76, 342-9Glaser et al. 2019, BMC Cancer, 19, 1271Haddow et al. 1944, Br Med J, 2, 393-8Hipolito Rodrigues & Gompel 2021, Women Health, 61, 3-14Hodis & Mack 2008, Menopause Manag, 17, 27-32Hodis & Sarrel 2018, Climacteric, 21, 521-528Hofling et al. 2007, Menopause, 14, 183-90Ingle et al. 1981, N Engl J Med, 304, 16-21Janssen 2021, Int J Mol Sci, 22Lalitkumar et al. 2023, Int J Mol Sci, 24Lauby-Secretan et al. 2016, N Engl J Med, 375, 794-8Li et al. 2017, Oncotarget, 8, 39896-39921Lobo et al. 2018, Obstet Gynecol, 132, 161-170Manson et al. 2013, JAMA, 310, 1353-68Manson et al. 2017, JAMA, 318, 927-938Meaidi et al. 2024, BMJ Med, 3, e000753Mikkola et al. 2016, Menopause, 23, 1199-1203Million Women Study Collaborators 2003, Lancet, 362, 419-27Mirkin 2018, Climacteric, 21, 346-354Montz et al. 2002, Am J Obstet Gynecol, 186, 651-7Murkes et al. 2012, Gynecol Endocrinol, 28 Suppl 2, 12-5Peethambaram et al. 1999, Breast Cancer Res Treat, 54, 117-22Santen et al. 2013, Horm Cancer, 4, 195-207Schernhammer & Hankinson 2005, J Natl Cancer Inst, 97, 1084-7Schernhammer et al. 2008, J Natl Cancer Inst, 100, 898-905Schierbeck et al. 2012, BMJ, 345, e6409Smith-Warner et al. 1998, JAMA, 279, 535-40Stute et al. 2018, Climacteric, 21, 111-122Tamimi et al. 2006, Arch Intern Med, 166, 1483-9U.S. Food and Drug Administration 2025, Drug Safety CommunicationVinogradova et al. 2020, BMJ, 371, m3873Viscoli et al. 2001, N Engl J Med, 345, 1243-9Writing Group for the Women's Health Initiative Investigators 2002, JAMA, 288, 321-33Book a consultation: withinyou.health/links
