Transfeminine HRT (Advanced)

Overview

Transfeminine hormone therapy (transfem HT) has two main goals: suppressing endogenous androgens (primarily testosterone) to levels in the cisgender female range, and raising estradiol to physiological female levels^[1]. Depending on the chosen protocol, these two goals can be achieved separately or simultaneously.

This guide covers the underlying hormonal mechanisms, all types of estrogens and their esters available, all types of antiandrogens with their efficacy profiles, risks and mechanisms of action, the use of progesterone, estradiol monotherapy, and how to interpret hormone panels.

If you haven't started HRT yet, I recommend starting with the beginner guide. If you need personalized help, you can reach out on our Discord.

Relevant hormonal physiology

Understanding HRT requires understanding the hypothalamic-pituitary-gonadal axis (HPG axis) and how androgens and estrogens interact with it.

The HPG axis and negative feedback

The hypothalamus secretes GnRH (gonadotropin-releasing hormone) in a pulsatile manner, which stimulates the pituitary gland to release LH (luteinizing hormone) and FSH (follicle-stimulating hormone). LH acts on the testicular Leydig cells to produce testosterone. Both estradiol and testosterone act negatively on the hypothalamus and pituitary gland, suppressing GnRH, LH, and FSH^[1].

In transfeminine HRT, estradiol at sufficient doses can suppress LH production and, therefore, testicular testosterone production. This is the basis of estradiol monotherapy.

Peripheral conversion and aromatization

Testosterone is converted into estradiol by the enzyme aromatase (present in adipose tissue, muscle, brain, and liver). DHT (dihydrotestosterone) is formed from testosterone by 5α-reductase and is the most potent androgen at the androgen receptor; it cannot be aromatized into estrogens. DHT is primarily responsible for androgenic alopecia, prostate development, and part of body hair growth. In transfeminine people, DHT can be generated from progesterone in a subset of individuals, through a mechanism known as the "backdoor pathway" (androgen backdoor pathway). This mechanism bypasses testosterone entirely as an intermediate step^[2]. In this group of people, the biochemical mechanism is as follows: Progesterone -> 17α-hydroxyprogesterone (17-OHP) via the enzyme CYP17A1 -> 5α-pregnane-17α-ol-3,20-dione, in which the enzyme 5-alpha reductase type 1 (SRD5A1) is involved -> 17-OH-allopregnanolone, in which the enzyme 3α-HSD (AKR1C2/4) is involved -> Androsterone, in which the previously mentioned enzyme CYP17A1 is involved -> Androstanediol -> DHT via the enzymes 17β-HSD type 3 or 17β-HSD and then a final oxidation (by RoDH/17β-HSD6). There is no conclusive information on why only a subset of people exhibit this mechanism so pronouncedly, but it is believed to be due to the body having high expression of the previously mentioned enzymes. In the transfeminine population this mechanism is described mainly in community experiences^[31]; there are no specific clinical studies confirming its frequency or relevance.

Receptors and tissue sensitivity

The effects of hormones depend on the density and sensitivity of their receptors in each tissue. The estrogen receptor (ER-α and ER-β) and the androgen receptor (AR) mediate the effects. Individual sensitivity to estrogens and androgens varies genetically, which explains why people with similar hormone levels have different physical responses.

SHBG (sex hormone-binding globulin)

SHBG is a transport protein synthesized in the liver. Hormones bound to it cannot cross cell membranes or activate their receptors, so the free fraction is the biologically active one. Androgens reduce SHBG production and estrogens increase it, so SHBG tends to rise with feminization^[4].

That has two distinct consequences for transfeminine HRT^[4]:

• Testosterone: SHBG binds T with higher affinity than estradiol, so when SHBG rises, the free fraction of T falls proportionally more. In transfeminine people this is advantageous: it is an antiandrogenic effect additional to HPG axis suppression (for example, contraceptives with ethinylestradiol, which raise SHBG about 4-fold, reduce the free fraction of T to one third). The effect is more marked with oral E2 (SHBG ×2–3) or with high-dose injectables (up to ×3) than with non-oral routes at levels ≤200 pg/mL (only ×1.1–1.5).
• Estradiol: the effect is much weaker, because E2 has less affinity for SHBG. At therapeutic non-oral levels (≤200 pg/mL) the reduction in the free fraction of E2 is minimal and clinically irrelevant: feminization and breast development are already maximal at low E2 levels (<50 pg/mL), as physiological puberty shows. Therefore, with therapeutic non-oral levels, SHBG ceases to be a problem for the efficacy of estradiol.

Lab panels usually measure total T; free T is less accessible. With high SHBG induced by E2, free T can be substantially lower than total T suggests.

Estrogens in transfeminine HRT

Types of estrogen

The estrogen used in transfeminine HRT is almost universally 17β-estradiol (the bioidentical human form). Synthetic estrogens such as ethinylestradiol (EE, found in contraceptives) were historically used, but they have fallen out of use in HRT because of their much higher thrombotic risk profile and because they are not detected on standard E2 panels. Ethinylestradiol is 100 to 200 times more potent than 17β-estradiol, and it is not destroyed by the liver when taken orally. For this reason, it has almost 1000 times more hepatic impact than E2, which includes a drastic increase in the production of clotting factors^[5][6].

Estradiol esters: mechanism and properties

Esters are prodrugs: estradiol molecules esterified at the C17 position with a fatty acid. When injected (usually in MCT or castor oil), they form a depot in muscle or subcutaneous tissue from which they are released slowly. Plasma esterases hydrolyze the ester, releasing active free estradiol. The length of the fatty acid's lipophilic chain determines the release rate and the half-life^[7][8].

Routes of administration

Intramuscular injection (IM)

Injection into muscle (glute, vastus lateralis of the thigh). Allows high and stable levels. Absorption somewhat faster than SubQ, which can produce a more pronounced initial peak depending on the ester. The depot disperses well in vascularized muscle tissue.

Subcutaneous injection (SubQ)

Injection into adipose tissue (abdomen, thigh, gluteal area). Absorption is somewhat slower and more sustained than IM with some esters, although in practice both routes achieve similar levels. The popular belief that SubQ EEn produces significantly higher E2 levels than IM at the same dose is not supported by the evidence: the largest comparative study (n=130) found no differences in the E2 or T levels reached between the two routes, with practically identical weekly doses (3.75 vs 4 mg)^[9], and a 2026 retrospective study (n=70) found, in an exploratory analysis, mean E2 levels lower with the SubQ route than with the IM route^[10]. The available data are scarce and discordant, so the prudent recommendation is to re-check levels 6–8 weeks after switching routes and adjust the dose according to the result, instead of assuming from the outset that the dose needs to be reduced. Less painful for many people, thinner needles (25–31G).

Oral (tablet/capsule)

Oral estradiol undergoes extensive hepatic first-pass metabolism: much of it is converted into estrone (E1) before reaching the systemic circulation^[6]. The E1:E2 ratio is reversed relative to normal physiology (E1 dominates). E2 levels are less predictable and more variable. It raises SHBG and clotting factors more than parenteral routes, increasing thrombotic risk^[5]. Generally not recommended as the primary route when another can be chosen.

Sublingual (tablet dissolved under the tongue)

Partially avoids hepatic first-pass metabolism through direct absorption into the bloodstream via the mucous membranes. Produces higher but shorter-lived peaks (half-life ~2–4 h). It is administered 2–4 times a day to maintain more stable levels. Better profile than oral, but with more variability than injectable^[11]. Useful when injectable is not accessible.

Transdermal (gel, patch, cream)

Direct absorption through the skin, avoiding hepatic first-pass metabolism. Patches have controlled release (daily or weekly). The gel is applied daily. Absorption varies according to the application site, skin hydration, and temperature. For patches, areas with fat have higher absorption. They can reach high levels if enough is applied. Low impact on SHBG and clotting factors^[12]. Disadvantage: inconsistent absorption between individuals, hard to predict levels. The scrotal/penoscrotal areas (in the case of cream or gel, or sprays such as Lenzetto) have much higher absorption than the skin of the arm (up to 5–8x)^[13].

Rectal (suppository/tablet)

Allows direct absorption, avoiding hepatic first-pass metabolism. Levels similar to sublingual but with a more sustained profile in some studies. Mainly used for progesterone (which has a very low and source-dependent oral bioavailability, on the order of 2% to 8%^[3])

Estradiol monotherapy (suppression without an AA)

With sufficiently high E2 levels (>200 pg/mL sustained, ideally >200–300 pg/mL), estradiol suppresses the HPG axis through a negative feedback effect, reducing LH and FSH and, consequently, testicular testosterone production to levels in the female range (<50 ng/dL, ideally <30 ng/dL)^[1].

Monotherapy with injectable EEn or EV is currently the most common protocol in DIY communities, because of its efficacy and simplicity. It requires sufficient doses to maintain elevated E2 levels constantly (not cycles with peaks and low troughs).

Advantages over using an AA: fewer medications, fewer side effects, less risk (without the specific adverse effects of AAs). The main goal is to achieve and maintain complete suppression, which may require some time of dose adjustment.

Not everyone achieves complete suppression with monotherapy. In people with very high testicular production or a limited individual response, it may be necessary to combine with an AA^[15].

Antiandrogens (AAs)

General mechanisms of AAs

Antiandrogens act through different mechanisms to reduce androgenic activity:

• Androgen receptor (AR) antagonists: directly block the receptor, preventing testosterone and DHT from exerting their effects (bicalutamide, flutamide, enzalutamide, spironolactone in part).
• Androgen synthesis suppressors: reduce testosterone production by acting on the HPG axis (GnRH analogs, cyproterone acetate through gonadotropic suppression).
• 5α-reductase inhibitors: block the conversion of testosterone into DHT (finasteride, dutasteride). They are not AAs proper but inhibitors of peripheral conversion.
• Mixed mechanism: spironolactone combines weak AR antagonism with a mild reduction in testosterone synthesis^[16].

Spironolactone

An aldosterone antagonist with secondary antiandrogenic activity. AA mechanism: weak AR antagonism and mild reduction in T synthesis^[17]. Widely used in the US because of availability and medical familiarity.

Cyproterone Acetate (CPA)

A synthetic progestogen with potent antiandrogenic activity. Mechanism: AR antagonism and gonadotropic suppression (acts on the HPG axis, reducing LH/FSH and therefore T synthesis). Very potent and effective^[18]. Widely used in Europe. Not commonly available in the US.

Bicalutamide

A pure androgen receptor antagonist (it does not reduce T levels, but rather blocks its action in tissues). It does not suppress androgen synthesis, so T and DHT levels may remain or even rise while their effects are blocked at the receptor level^[20].

GnRH analogs (agonists and antagonists)

GnRH agonists (leuprorelin, triptorelin, goserelin, histrelin) act paradoxically: by administering GnRH continuously (not pulsatilely), they desensitize the pituitary receptors, inhibiting the release of LH and FSH and, therefore, suppressing testicular T production to castration levels. Initially they produce a transient "flare" (a rise in T for 1–2 weeks) before suppression^[21].

GnRH antagonists (degarelix, relugolix) block the GnRH receptor directly without the initial flare. Newer and generally more expensive.

Rectal progesterone as a mild AA

Progesterone at high doses has antigonadotropic activity (suppresses LH/FSH), which contributes to reducing T. Its rectal use allows greater bioavailability than oral (from 5-8% to almost 100%). At doses of 200 mg rectally at night it can contribute to androgen suppression as a complementary component. This is discussed further in the Progesterone section.

Other antiandrogens and strategies

5α-reductase inhibitors (5-ARIs): finasteride and dutasteride

They are not AAs proper: they do not block the AR or reduce total T. They inhibit the conversion of T into DHT, which is the most potent androgen at peripheral androgen receptors (skin, scalp, prostate).

Finasteride: mainly inhibits 5α-reductase type 2. Reduces DHT ~70%. Useful for androgenic alopecia and stubborn body hair in the context of partially suppressed T. Dose: 1–5 mg/day^[24].

Dutasteride: inhibits 5α-reductase types 1 and 2. Reduces DHT ~90–95%. Greater efficacy for alopecia. Dose: 0.5 mg/day^[24].

In transfeminine HRT with good T suppression, DHT will already be very low, so 5-ARIs contribute little. They are more relevant when T is partially suppressed and DHT-dependent symptoms persist.

Flutamide

A first-generation nonsteroidal AR antagonist, the precursor of bicalutamide. Notably worse hepatotoxicity profile than bicalutamide. Practically abandoned in transfeminine HRT in favor of bicalutamide. Not recommended.

Enzalutamide, apalutamide, darolutamide

Last-generation AR antagonists used in castration-resistant prostate cancer. Greater potency than bicalutamide, but very high cost and a more marked side-effect profile (risk of seizures with enzalutamide). Insufficient evidence in routine transfeminine HRT. They are mentioned for completeness; they are not commonly used.

Drospirenone

A synthetic progestogen with antimineralocorticoid and moderate antiandrogenic activity. Present in contraceptives. It can be used as a mild adjunct AA, but its antiandrogenic efficacy is lower than CPA or bicalutamide. Safer profile than CPA regarding meningioma risk.

Combinations and mixed strategies

Some protocols combine mechanisms: for example, bicalutamide (AR blockade) + moderate doses of E2 (partial T suppression). Or low-dose CPA + E2 as monotherapy. Combining mechanisms can allow reducing the dose of each component and, with it, the side effects of each one.

Bicalutamide post-Tanner 3: advanced use

One of the most debated and relevant uses in advanced transfeminine HRT is that of bicalutamide after having reached Tanner stage 3 of breast development (in which the areola and nipple form a clearly differentiated secondary projection).

Stages of breast development (Tanner scale)

Why is bicalutamide used post-Tanner 3?

The hypothesis, derived from observations in the context of transfeminine HRT in adolescents and from studies of breast sensitivity, is the following: during early breast development (Tanner 2–3), the breast tissue is very sensitive to androgens, which can inhibit glandular growth. Androgenic exposure during this critical phase may limit the final development potential^[22].

Once Tanner 3 has been reached, the glandular tissue is already established and the risk of androgenic inhibition of development is lower. At this point, some people on E2 monotherapy (which may not completely suppress T) or on AAs that do not directly block the AR could benefit from adding bicalutamide to block any residual androgenic effect on the breast tissue and other sensitive tissues.

Mechanism and theoretical rationale

Bicalutamide, being a pure AR antagonist, blocks the action of any residual T or DHT directly at the receptors of the target tissues (breast, skin, scalp, etc.). This can be particularly useful in people who:

• Have partially suppressed T but not in the full female range (>50 ng/dL)
• Experience residual androgenic effects (hair, alopecia, acne) despite adequate E2
• Wish to optimize breast development without increasing the E2 dose or adding a suppressive AA (CPA) that has more side effects

Evidence and limitations

Direct evidence in the adult transfem population post-Tanner 3 is limited; the hypothesis is extrapolated from studies in different contexts (oncology, pediatric endocrinology, pharmacology). There is no randomized clinical trial that has shown that adding bicalutamide post-Tanner 3 improves final breast development compared with not doing so.

The idea of using Tanner stage 3 as a milestone to adjust androgen blockade (adding bicalutamide from that point on, or, in the inverse variant, keeping it until that stage is reached) has been circulating for years in DIY communities based on anecdotal clinical observations (r/DrWillPowers^[29], r/TransDIY^[30]). It should therefore be treated as a community hypothesis without experimental support.

Suggested protocol (informational)

When bicalutamide is used in this context:

• Typical dose: 25 mg/day. Some people use 12.5 mg/day as the minimum effective dose.
• The E2 protocol is maintained without significant changes.
• Liver monitoring (ALT/AST) at 3 months after starting and thereafter every 6–12 months.
• Duration: variable; many people keep it until the desired breast development is complete or indefinitely if they tolerate it well and levels are adequate.
• Remember that circulating T and DHT do not fall with bicalutamide (they may rise): T lab results are not indicators of blocking efficacy in this case.

Progesterone

Progesterone (P4) is the endogenous progestational hormone. In cis women it is present mainly in the luteal phase of the menstrual cycle. Its role in transfeminine HRT is controversial but increasingly studied.

Bioidentical progesterone vs. synthetic progestogens

It is essential to distinguish between:

• Bioidentical (micronized) progesterone: identical to human P4. Examples: Seidigestan, Utrogestan, Prometrium. Acts on progesterone receptors (PR) and not on the AR.
• Synthetic progestogens: progesterone analogs (medroxyprogesterone acetate, norethisterone acetate, drospirenone, levonorgestrel, CPA...). They have different activity profiles, many with additional androgenic or antiandrogenic effects. They are NOT equivalent to bioidentical P4 in their effects on the PR or in their safety profile.

Effects of progesterone in transfeminine HRT

The evidence is mixed and partly based on community observations^[22]. The potentially beneficial effects reported include:

• Improved breast development in some people (especially breast shape and the areola-nipple complex), with a possible effect on Tanner stage
• Improved libido (P4 can act on neurosteroid receptors and has effects on sexual desire)^[23]
• Effects on sleep (allopregnanolone, a P4 metabolite, has GABAergic action, producing drowsiness)
• Contribution to androgen suppression (antigonadotropic effect at high doses)
• Possible cardioprotective and bone effects (less studied in transfems)

Route of administration: why rectal?

Oral progesterone has a very low bioavailability and an extensive hepatic first pass that converts it into metabolites (5α- and 5β-reduced), reducing active circulating P4. The metabolite allopregnanolone (5α-reduced) has sedative/anxiolytic activity (GABA-A agonist), which explains the drowsiness produced by oral progesterone^[6].

The rectal route (micronized tablet/capsule inserted rectally) largely avoids hepatic first pass, producing significantly higher circulating P4 levels (comparable to the mid-luteal phase) with the same 200 mg that orally would produce much lower levels. This makes the rectal route pharmacologically superior for achieving systemic P4 levels^[3].

When to consider adding progesterone

The most common recommendation in the community and among some progressive endocrinologists is to wait at least 1 year of HRT with E2 before adding progesterone, to give breast tissue time to develop in an estrogenic environment first. Adding P4 too early can (theoretically) prematurely advance Tanner stage to 5 before there is enough glandular tissue, limiting the final result^[22].

Standard dose: 200 mg at night via the rectal route^[8]. The oral route is not recommended if the goal is a systemic P4 effect; it can be reserved if the sedative effect is what is sought.

Target hormone levels

Target ranges are references, not absolute truths^[1]. Individual tissue response varies, and levels should be interpreted together with the symptoms and effects observed.

When to measure and how to interpret

With injectables, the blood draw should be done at trough (the day before or the same day as the next injection, before injecting), to measure the minimum maintained level. Post-injection peaks are temporary and do not represent the sustained mean level. With transdermal, gel, or patch, measure at mid-application or at the end (before the next application).

With sublingual, levels fluctuate a lot; measure 2–4 h post-dose for peak or just before the next dose for trough.

Advanced protocols

Protocol 1: Monotherapy with injectable EEn (SubQ or IM)

The most popular protocol in DIY communities at present.

• Medication: Estradiol enanthate (EEn) in oil (typically 40/50 mg/mL)
• Starting dose: 5–6 mg weekly^[14]
• Frequency: every 7 days
• Route: SubQ (preferred for greater level stability) or IM
• Goal: trough E2 >200 pg/mL, T <50 ng/dL
• Adjustment: if T is not adequately suppressed at 3 months, increase the dose; if E2 is very high and there are side effects, reduce it
• Consideration: some people do not achieve complete T suppression with monotherapy and require an AA

Protocol 2: E2 + low-dose CPA

A classic protocol in Europe. Effective and well studied. Low-dose CPA minimizes risks.

• Injectable or transdermal E2 at moderate doses (target trough E2 100–200 pg/mL)
• CPA: 6.25–12.5 mg/day (can be done with 50 mg tablets split into quarters/eighths)
• Monitoring: prolactin, liver enzymes, mood
• CPA duration: many people reduce or withdraw CPA when E2 is enough for suppression on its own

Protocol 3: E2 + Bicalutamide

Useful when CPA is not available or is contraindicated, or a pure AR antagonist is preferred.

• Injectable or transdermal E2 at doses sufficient to obtain feminization
• Bicalutamide: 25–50 mg/day
• Free T will remain elevated; this is expected.
• The goal in this protocol is to block the tissue action of T, not to reduce its serum level
• Monitoring: liver ALT/AST

Protocol 4: Injectable E2 + Bicalutamide post-Tanner 3

An advanced optimization protocol for people on E2 monotherapy who have reached Tanner 3 and wish to enhance residual androgen blockade.

• Continue the existing E2 protocol without changes
• Add bicalutamide 12.5–25 mg/day
• Evaluate at 3–6 months: effects on hair, alopecia, skin, breasts

Protocol 5: E2 + Rectal progesterone (late phase)

For people with >1–2 years of HT who wish to add progesterone.

• Keep E2 at established levels
• Add rectal micronized P4 200 mg at night
• Evaluate: sleep, libido, breast changes, mood
• There are no very useful laboratory markers for evaluating subjective efficacy; be guided by symptoms

Protocol for transitioning from SubQ to IM or vice versa

When switching between SubQ and IM with the same ester, E2 levels should not vary systematically (see routes of administration). It is recommended to keep the dose, re-check at 6–8 weeks, and adjust according to the result.

Blood tests: interpretation

Lab panels are the main tool for monitoring HRT. Here we detail what to request, when, and how to interpret it^[25][27][28].

Basic hormone panel in transfem HT

• Estradiol (E2): central marker of estrogen therapy
• Total testosterone: marker of androgen suppression
• LH and FSH: indicators of HPG axis status
• SHBG: to calculate free testosterone if necessary and evaluate the hepatic effect of E2
• Prolactin: especially if CPA is used or if there are symptoms suggestive of hyperprolactinemia

Expanded panel according to medication

Specific interpretation of bicalutamide on lab panels

With bicalutamide, serum T should NOT be interpreted as with other AAs. T may be in the male range or even elevated (reflex rise due to loss of AR negative feedback in the hypothalamus). This is normal and expected. Treatment success is assessed by tissue effects (feminization, breast growth), NOT by the blood T level.

LH may also be elevated with bicalutamide (through the same feedback-blocking mechanism). This indicates nothing relevant.

Free vs. total testosterone

Total T measures all the T in the blood. Free T (not bound to SHBG) is the biologically active fraction. With high SHBG levels (induced by E2), free T can be much lower than total T, even when total T is in the low-male range. In people with very high SHBG (due to oral E2 or high doses of injectable E2), free T may be in the female range even though total T is borderline.

Risks, side effects, and monitoring

Thromboembolic risk

The risk of deep vein thrombosis (DVT) and pulmonary embolism (PE) is the most serious risk of transfeminine HRT. It varies significantly depending on the E2 route of administration^[5]:

• Oral E2: higher risk (hepatic first pass increases clotting factors)
• Injectable, transdermal, sublingual E2: considerably lower risk
• Ethinylestradiol (EE): the highest risk of all; do not use in transfem HRT

Factors that increase risk: smoking, obesity, prolonged immobility, hereditary thrombophilia, recent surgery, advanced age. Screening for thrombophilia before starting HRT is advisable in people with a family history of thrombosis^[25].

Bone health

Estrogens are essential for maintaining bone mineral density (BMD). In transfem HRT with adequate E2 levels, the risk of osteoporosis is low. The risk increases if there are prolonged periods with insufficient E2 or if puberty blockers are used without adequate simultaneous estrogen supplementation. With long-term GnRH analogs without adequate E2, bone loss can be significant.

Cardiovascular health

Transfem HRT can affect the lipid profile: E2 tends to raise HDL and lower LDL (beneficial), but it can also raise triglycerides. The overall cardiovascular risk in trans women on well-monitored HRT is debated; some studies suggest it may be higher than in cis women but lower than in cis men, although long-term data are limited. Monitoring of the lipid profile (total cholesterol, HDL, LDL, TG) annually.

Liver health

Injectable or transdermal E2 have minimal hepatic impact. The main risk comes from AAs: CPA (hepatotoxicity at high doses, rare at low doses), bicalutamide (rare but real idiosyncratic hepatotoxicity, better documented at high oncological doses), flutamide (high hepatotoxicity; obsolete). Monitoring with ALT/AST is essential when using these medications.

Fertility

Prolonged suppression of spermatogenesis may be partially reversible upon stopping HRT, but full recovery is not guaranteed, especially after several years. If preserving fertility is desired, sperm cryopreservation before starting HRT is the recommended option. Once HRT has started, recovery of fertility is possible but uncertain.

Mental health

HRT generally has positive effects on psychological well-being in trans people. However, hormonal fluctuations (poor dose adjustment, periods of low levels), the use of CPA (risk of depression), or excessively high or low E2 levels can cause emotional instability. Monitor mood and adjust the protocol if necessary.

Genital atrophy

Androgen suppression produces atrophy of the penile and scrotal tissue: the skin becomes thinner, the tissue loses elasticity, and it can become painful over time. This is expected and partly reversible, but it can be problematic, especially if vaginoplasty is planned (which requires enough tissue for neovaginal construction).

Prevention

• Maintain regular erections (at least 2 times a week). Erections keep the tissue oxygenated and elastic. They do not require finishing in orgasm.
• If there is severe erectile dysfunction, the use of PDE5 inhibitors (sildenafil, tadalafil) can help maintain erections for this purpose.

Treatment of established atrophy

• Topical testosterone cream (low dose): the use of 0.5–2% T creams on the affected tissue (without significant systemic absorption if used locally and in small amounts) can reverse atrophy without affecting systemic feminization. It must be prescribed and monitored by a physician.
• Topical estriol: estriol creams can improve lubrication and the health of mucosal tissue without a significant systemic effect.
• Tissue expanders: if vaginoplasty is planned, surgeons usually recommend tissue expansion techniques before the procedure if there is significant atrophy.

Atrophy and vaginoplasty

Severe atrophy can complicate vaginoplasty. The amount of tissue available determines the possible vaginal depth. If surgery is planned, tell the surgeon in advance so they can plan the management of atrophy.

Expected changes with transfem HRT

For reference, the following table summarizes typical physical changes, onset times, and time to maximum effect.

Source: Transfemscience^[1] (table of effects and timelines of transfeminine HRT; reproduced from clinical literature with modifications).

Glossary

E2

Estradiol (17β-estradiol), the main bioidentical estrogen.

EEn

Estradiol enanthate, an injectable ester with a half-life of ~5–7 days.

EV

Estradiol valerate, an injectable ester similar to EEn.

EC

Estradiol cypionate, an injectable ester with a half-life of ~8–14 days.

T

Testosterone.

DHT

Dihydrotestosterone, the most potent androgen at the androgen receptor; a product of 5α-reductase.

AR

Androgen receptor.

ER

Estrogen receptor (α and β).

AA

Antiandrogen.

CPA

Cyproterone acetate, a potent antiandrogenic progestogen.

Bica

Bicalutamide, a pure AR antagonist.

5-ARI

5α-reductase inhibitor (finasteride, dutasteride).

GnRH

Gonadotropin-releasing hormone.

LH

Luteinizing hormone.

FSH

Follicle-stimulating hormone.

SHBG

Sex hormone-binding globulin.

HPG

Hypothalamic-pituitary-gonadal axis.

P4

Progesterone.

SubQ

Subcutaneous injection.

IM

Intramuscular injection.

DIY

Do It Yourself; self-managed HRT without a prescription.

Reflex rise

Reactive elevation of T (and LH) when using AR antagonists such as bicalutamide, due to loss of androgenic negative feedback on the HPG axis.

Hepatic first pass

Metabolism of the drug in the liver before it reaches the systemic circulation when administered orally.

Tanner

Marshall and Tanner scale of pubertal development stages (1–5).

BMD

Bone mineral density.

DVT / PE

Deep vein thrombosis / Pulmonary embolism.

Sources

Community sources

• [1] Transfemscience -- "An Introduction to Hormone Therapy for Transfeminine People" (Aly). General reference article: physiology, target levels, gonadal suppression, routes of administration, medications, monitoring, and the timeline table of changes. It is the direct source of the expected changes table. transfemscience.org/articles/transfem-intro/
• [7] Transfemscience -- "An Informal Meta-Analysis of Estradiol Curves with Injectable Estradiol Preparations" (Aly). Compared curves and half-lives of the injectable esters. transfemscience.org/articles/injectable-e2-meta-analysis/
• [8] diyhrt.wiki -- "Transfeminine DIY HRT: the Ultimate Guide". Ester half-lives (EV ~3.0 d, EC ~6.7 d, EEn ~4.6 d), dosing schedules, monitoring, and risks. diyhrt.wiki/transfem
• [11] Transfemscience -- articles on the sublingual route: "An Exploration of Sublingual Estradiol as an Alternative to Oral Estradiol in Transfeminine People" (Sam) and "Sublingual Administration of Oral Estradiol Valerate Tablets" (Aly). transfemscience.org/articles/sublingual-e2-transfem/
• [12] Transfemscience -- "A Comparison of Oral and Transdermal Estradiol in Transfeminine Hormone Therapy" (Sam). transfemscience.org/articles/oral-vs-transdermal-e2/
• [13] Transfemscience -- "Genital Application via the Scrotum and Neolabia for Greatly Enhanced Absorption of Transdermal Estradiol" (Aly). Much higher absorption on scrotal/neolabial skin. transfemscience.org/articles/genital-e2-application/
• [3] Transfemscience -- "Oral Progesterone Achieves Very Low Levels of Progesterone and Has Only Weak Progestogenic Effects" (Aly). Pharmacokinetics of oral/rectal progesterone and its metabolites. transfemscience.org/articles/oral-p4-low-levels/
• [4] Transfemscience -- "The Interactions of Sex Hormones with Sex Hormone-Binding Globulin and Relevance for Transfeminine Hormone Therapy" (Aly). transfemscience.org/articles/shbg-unimportant/
• [5] Transfemscience -- "Estrogens and Their Influences on Coagulation and Risk of Blood Clots" (Aly). Includes the hepatic profile of ethinylestradiol versus 17β-estradiol and the thromboembolic risk by route of administration. transfemscience.org/articles/estrogens-blood-clots/
• [17] Transfemscience -- "A Review of Studies on Spironolactone and Testosterone Suppression..." (Aly). transfemscience.org/articles/spiro-testosterone/
• [18] Transfemscience -- "Low Doses of Cyproterone Acetate Are Maximally Effective for Testosterone Suppression in Transfeminine People" (Aly). transfemscience.org/articles/cpa-dosage/
• [19] Transfemscience -- "Recent Developments on Cyproterone Acetate and Meningioma Risk Out of France and Implications for Transfeminine People" (Aly). transfemscience.org/articles/cpa-meningioma/
• [20] Transfemscience -- "Bicalutamide and its Adoption by the Medical Community for Use in Transfeminine Hormone Therapy" (Aly). transfemscience.org/articles/bica-adoption/
• [21] Transfemscience -- "Puberty Blockers: A Review of GnRH Analogues in Transgender Youth" (Mitzi). transfemscience.org/articles/puberty-blockers/
• [22] Transfemscience -- "A Comprehensive Review of the Potential of Progestogens for Enhancing Breast Development in Transfeminine People" (Aly). Review of the evidence (mostly negative) on progesterone and breast development. transfemscience.org/articles/progestogens-breast-dev/
• [23] Transfemscience -- "The Influence of Progesterone and Other Progestogens on Sexual Desire and Function" (Aly). transfemscience.org/articles/progestogens-sexual-desire/
• [24] Transfemscience -- "A Review of Pharmaceutical Interventions for Scalp Hair Loss and Implications for Transfeminine People" (Sam). transfemscience.org/articles/hair-loss/
• [29] r/DrWillPowers -- "Bicalutamide Or spironolactone" (community discussion thread on the "E2 + bicalutamide until Tanner 3" approach). reddit.com/r/DrWillPowers/comments/ftf0s0/
• [30] r/TransDIY -- "Bicalutamide monotherapy and breast growth" (community discussion thread on bicalutamide and breast development/Tanner). reddit.com/r/TransDIY/comments/1hcfmw2/
• [31] r/AskMtFHRT -- "Progesterone is a 'backdoor pathway' for DHT?" (community discussion thread on the conversion of progesterone into DHT). reddit.com/r/AskMtFHRT/comments/jpuf9c/

Clinical literature and guidelines

• [2] Miller WL, Auchus RJ -- "The Molecular Biology, Biochemistry, and Physiology of Human Steroidogenesis and Its Disorders" (Endocrine Reviews, 2011; 32(1):81–151). Reference for the alternative androgen synthesis pathway (backdoor pathway). Full text free at PMC. pubmed.ncbi.nlm.nih.gov/21051590/
• [6] Kuhl H -- "Pharmacology of Estrogens and Progestogens: Influence of Different Routes of Administration" (Climacteric, 2005; 8(Suppl 1):3–63). Pharmacological reference on routes of administration, hepatic first pass, and metabolism of estrogens and progesterone. Local PDF · doi.org/10.1080/13697130500148875
• [9] Herndon JS et al. -- "Comparison of the Subcutaneous and Intramuscular Estradiol Regimens" (2023; n=130). No differences in the proportion of patients reaching therapeutic E2 levels between SC and IM; SC might achieve them with somewhat lower weekly doses (3.75 vs 4 mg). pubmed.ncbi.nlm.nih.gov/36868378/
• [10] Poage AC et al. -- "Comparison of Subcutaneous Versus Intramuscular Estradiol Administration for Feminizing Gender-Affirming Hormone Therapy" (Pharmacy, 2026; 14(1):13; n=70). Exploratory analysis: significantly lower E2 levels with the SC route. Local PDF · doi.org/10.3390/pharmacy14010013
• [14] Rothman MS et al. -- "The Use of Injectable Estradiol in Transgender and Gender Diverse Adults: A Scoping Review of Dose and Serum Estradiol Levels" (Endocrine Practice, 2024; 30:870–878). pubmed.ncbi.nlm.nih.gov/38782202/
• [15] Slack DJ et al. -- "Examining the Influence of the Route of Administration and Dose of Estradiol on Serum Estradiol and Testosterone Levels in Feminizing Gender-Affirming Hormone Therapy" (Endocrine Practice, 2025; 31:19–27). pubmed.ncbi.nlm.nih.gov/39401697/
• [16] Angus LM et al. -- "A Systematic Review of Antiandrogens and Feminization in Transgender Women" (Clinical Endocrinology, 2021; 94:743–752). pubmed.ncbi.nlm.nih.gov/32926454/
• [25] Hembree WC et al. -- "Endocrine Treatment of Gender-Dysphoric/ Gender-Incongruent Persons: An Endocrine Society Clinical Practice Guideline" (2nd version, JCEM, 2017). Local PDF · doi.org/10.1210/jc.2017-01658
• [26] Coleman E et al. -- "Standards of Care for the Health of Transgender and Gender Diverse People, Version 8" (WPATH SOC8, 2022). Local PDF (ES) · Local PDF (EN) · doi.org/10.1080/26895269.2022.2100644
• [27] UCSF Center of Excellence for Transgender Health -- "Guidelines for the Primary and Gender-Affirming Care of Transgender and Gender Nonbinary People" (Deutsch, ed.). transcare.ucsf.edu/guidelines
• [28] diyhrt.wiki -- "Blood tests". Recommended lab panel and trough/peak interpretation. diyhrt.wiki/bloodtests

Access to paywalled articles

Some PDFs are hosted locally and linked alongside each reference (fuentes/pdfs/). The rest of the cited papers are behind a paywall. The community (Transfemscience included) accesses them through Sci-Hub, whose mirror domains rotate every so often. The updated list is maintained in the Wikipedia article and on r/scihub. Equivalent alternatives: Library Genesis and Anna's Archive.

Useful tools from the same community sources: injectable estradiol level simulator (Transfemscience), estrannai.se, and the repository of pharmaceutical sources hrt.coffee.