Progesterone: the quiet half of hormone therapy.
Progesterone protects the uterine lining during estrogen therapy — and the specific progestogen chosen influences breast safety, sleep, and side effects.
Why estrogen alone isn't enough if you have a uterus
Unopposed estrogen stimulates the uterine lining and, over time, raises the risk of endometrial hyperplasia and cancer. A progestogen protects the lining. If you have had a hysterectomy, you generally do not need one — which is why "estrogen alone" and "combined" therapy have different risk profiles.
Which progestogen — and why it matters
Progestogens are not interchangeable. Micronized progesterone — chemically identical to the hormone the ovary produces — appears to carry less breast cancer risk than older synthetic progestins and is usually our first choice. Many women also notice it helps sleep when taken at night. Alternatives include dydrogesterone, a levonorgestrel IUD (which protects the uterus while delivering hormone locally), and conjugated estrogens with bazedoxifene, which protects the uterus without any progestogen at all.
Side effects and fine-tuning
Bloating, breast tenderness, or mood effects early in treatment usually respond to a change in dose, timing, or the specific progestogen. There are many options; finding the right fit sometimes takes an iteration or two, and that iteration is part of the plan — not a sign the plan failed.