Estradiol and progesterone: why most hormone therapy uses both

Why two hormones are needed

Before menopause the ovaries make both estrogen and progesterone, and the two work as a pair: estrogen builds up the lining of the uterus each month, and progesterone keeps that growth in check and sheds it. When the ovaries slow down, both fall. Hormone therapy replaces the estrogen because that is what drives the symptoms; it adds progesterone because estrogen on its own, in a woman who still has a uterus, keeps thickening the lining with nothing to hold it back.

That is why most menopause hormone therapy is a patchwork: an estrogen patch or gel from one prescription, a progesterone capsule from another, sometimes a separate vaginal cream. The BaselineRx protocol puts the pieces your clinician chooses into one kit, so there is one checkout and one pharmacy order, with the forms and strengths set by your intake and confirmed by a US-licensed clinician.

What estradiol does

Estradiol is the main estrogen your ovaries made before menopause, and bioidentical estradiol is the same molecule. It is the component that addresses the whole cluster of symptoms: hot flashes and night sweats, sleep that is broken by them, mood swings and irritability, brain fog, joint aches, and changes in skin, hair and vaginal tissue.

Current menopause-society guidance holds that hormone therapy remains the most effective treatment for hot flashes and night sweats, and that for most healthy women under 60 or within 10 years of the start of menopause, the benefits outweigh the risks. Systemic estradiol is also approved to prevent postmenopausal bone loss, though it is not a treatment for osteoporosis that is already established.

In the BaselineRx protocol estradiol is given through the skin by default: a twice-weekly patch, a daily gel, or a compounded cream. Transdermal estrogen does not pass through the liver first, and the clinical team prefers it because it carries a lower blood-clot risk and less effect on cholesterol than oral estrogen. An oral tablet is reserved for women who have had side effects from topical estrogen and have no blood-clot risk factors.

What progesterone does

Progesterone’s job in hormone therapy is protective. Estrogen taken alone stimulates the lining of the uterus (the endometrium); over time that can lead to endometrial hyperplasia and, with it, a higher risk of endometrial cancer. Adding a progestogen counters that growth. This is the reason the FDA label for estradiol warns against unopposed estrogen in women who have a uterus, and why micronized progesterone is approved specifically to prevent endometrial hyperplasia in postmenopausal women taking estrogen.

Micronized progesterone is the bioidentical form: it is chemically identical to the progesterone the ovaries make, as opposed to synthetic progestins such as medroxyprogesterone acetate. It comes as an oral capsule taken at bedtime, because it can cause drowsiness or dizziness in some women, which is also why many women find it helps them sleep. The capsules contain peanut oil, so they cannot be used by anyone with a peanut allergy; the intake asks.

Progesterone does not treat hot flashes on its own in this protocol and is not prescribed by itself. It is the partner to estradiol.

Who needs progesterone: uterus vs hysterectomy

The rule is simple and the intake applies it. If you still have a uterus, you need progesterone alongside estradiol, unless you have previously had a poor reaction to micronized progesterone, in which case your clinician discusses an estrogen-only plan with you and the risk it carries. If you have had a hysterectomy, there is no lining to protect, so progesterone is optional: the protocol still offers it when you report sleep difficulty or breast tenderness, because it can help with those, and leaves it out otherwise.

Women who are already on hormone therapy and switching to BaselineRx keep whatever they currently take; the intake asks whether progesterone is part of your regimen and matches it.

The forms the pair comes in

Estradiol comes in four forms and progesterone in one, with one exception where the two are combined. Your clinician helps you choose, and you can state a preference during intake.

How the pair is dosed

Your intake sets the estradiol strength. In the BaselineRx protocol, new patients whose symptoms began less than five years ago usually start on the standard dose (the 0.05 mg/day patch, 0.5 mg gel or cream), and those whose symptoms began more than five years ago start on the low dose (0.025 mg/day patch, 0.25 mg gel or cream). Higher strengths are reserved for women with added factors such as surgical menopause or osteoporosis risk.

The progesterone strength follows the estradiol strength. 100 mg nightly is the standard and is used in every new-patient kit; 200 mg is paired with the higher estradiol doses so the lining stays protected. The FDA label for micronized progesterone describes a cyclic regimen of 200 mg for 12 days of each month; continuous daily dosing, which the BaselineRx protocol uses, is the other regimen recognised in menopause-society guidance and avoids a monthly withdrawal bleed for most women.

Unlike weight-loss medication, hormone therapy is not usually titrated up over time; most women stay on their starting dose. Your clinician checks in at two and six weeks and reviews your dose with you around month three. The guiding rule from the product labels is the lowest effective dose, reassessed periodically. No lab work is needed to start.

Risks and side effects of combined hormone therapy

The most common side effects reported with estradiol are headache, breast tenderness, upper respiratory and sinus symptoms, back pain, low mood, and irregular spotting or bleeding; skin irritation under a patch is common and usually settles with site rotation. With micronized progesterone the most frequently reported were headache, breast tenderness, joint pain, depression, dizziness, abdominal bloating, and drowsiness after the dose, which is why it is taken at bedtime. Tell your clinician about any bleeding you were not expecting.

Combined estrogen-plus-progestogen therapy carries serious risks. The FDA boxed warning for estrogen products covers stroke, blood clots, probable dementia in women over 65, and, for estrogen plus progestin, invasive breast cancer and heart attack; it states that estrogen, with or without progestin, should not be used to prevent heart disease or dementia. Much of that evidence comes from the Women’s Health Initiative trial of oral conjugated estrogens with a synthetic progestin; whether bioidentical, transdermal regimens carry the same risks is an open question in the literature, and the clinical team does not claim they are safer in that respect. Hormone therapy is not prescribed for women with a history of breast or uterine cancer, blood clots, stroke or heart attack, unexplained vaginal bleeding, active liver disease, or who may be pregnant. The full safety information is at the bottom of this page.

Getting estradiol and progesterone prescribed online

BaselineRx is a telehealth platform. You complete a private online intake covering your symptoms, your health history, whether you still have a uterus, and any past reaction to progesterone; it takes about two minutes and no labs are needed. A US-licensed clinician from Arora Health & Aesthetics reviews it, typically within one business day, and decides whether hormone therapy is appropriate and which estradiol form, estradiol strength and progesterone strength fit you.

If you are approved, your kit is dispensed by a licensed US pharmacy and shipped free and discreetly to your door as one order, with check-ins at two and six weeks and a dose review around month three. If you are not approved, nothing ships and you are not charged. Availability varies by state and is confirmed during your intake.