Progesterone
Overview
Progesterone is a naturally occurring female hormone that some trans women add to their HRT regimen. While not strictly necessary for feminisation, many report benefits for breast maturation, libido, mood, and sleep.
| Property | Details |
|---|---|
| Drug class | Progestogen |
| Mechanism | Binds progesterone receptors; may support breast maturation |
| Half-life | 16–20 hours (oral) |
| Typical dose | 100–200 mg/day |
| Common brands | Utrogestan, Prometrium |
Potential Benefits
| Benefit | Evidence Level | Notes |
|---|---|---|
| Breast maturation (Tanner 4–5) | Anecdotal / limited | May help with breast rounding and fullness |
| Increased libido | Anecdotal | Many report increased sexual desire |
| Improved sleep | Anecdotal | Calming effect for some |
| Mood improvement | Mixed | Some feel better; others feel worse |
| Reduced anxiety | Anecdotal | Calming effect reported |
The evidence for progesterone
The evidence for progesterone's benefits in trans women is largely anecdotal. Clinical trials are limited and results are mixed. Some trans women report significant benefits; others report no effect or negative side effects. It is worth trying if you're curious, but not essential.
Timing
Most clinicians who prescribe progesterone recommend:
- Wait 6–12 months after starting estrogen before adding progesterone
- This allows baseline breast development to establish first
- Starting too early may stunt breast growth (theoretical concern, not proven)
Dosing
| Level | Dose | Route | Notes |
|---|---|---|---|
| Starting | 100 mg/day | Oral or rectal | Assess tolerance |
| Typical | 200 mg/day | Oral or rectal | Split 100 mg AM + 100 mg PM if needed |
| Maximum | 300 mg/day | Rarely needed |
Routes of Administration
| Route | Bioavailability | Pros | Cons |
|---|---|---|---|
| Oral | ~10% | Convenient | First-pass liver metabolism; drowsiness |
| Rectal | ~25% | Better absorption, less drowsiness | Less convenient |
| Sublingual | Varies | Avoids first-pass | Difficult (pills crush easily) |
Rectal administration
Many trans women prefer rectal administration (inserting the capsule like a suppository) because:
- Higher bioavailability
- Fewer sedative effects
- Less liver metabolism
To use rectally: insert the capsule about 1–2 inches before bed. The capsule shell dissolves and the progesterone is absorbed.
Side Effects
| Side Effect | Frequency | Notes |
|---|---|---|
| Drowsiness/sedation | Very common (oral) | Take at bedtime |
| Mood swings | Some | Can cause depression in susceptible people |
| Weight gain | Some | Progestogenic effect |
| Breast tenderness | Common | Similar to menstrual breast pain |
| Bloating | Some | Temporary |
| Headaches | Occasional |
Progesterone can worsen depression
If you have a history of depression, monitor your mood carefully when starting progesterone. Some people experience significant mood decline. Stop and consult a provider if this happens.
What Form of Progesterone to Use
| Type | Recommendation | Notes |
|---|---|---|
| Micronised progesterone | ✅ Recommended | Bioidentical; safest option |
| Medroxyprogesterone acetate (MPA, Provera) | ❌ Not recommended | Synthetic progestin; less favourable side effect profile |
| Dydrogesterone | ⚠️ Limited data | Synthetic progestin; less studied in trans women |
| Norethisterone | ❌ Not recommended | Synthetic; androgenic side effects |
Does Progesterone Actually Help Breast Growth?
This is one of the most debated topics in trans feminine HRT.
- Theory: Progesterone is involved in breast maturation (alveolar development) in cisgender women during puberty
- Anecdotal evidence: Many trans women report breast rounding and fullness after adding progesterone
- Scientific evidence: Limited. A few small studies suggest possible benefit; larger trials have not been done
- Verdict: Worth trying, but not guaranteed. If it works for you, you'll likely notice within 2–3 months
References
Wierckx K, et al. (2014). Effects of progesterone in trans women: a systematic review.
Deutsch MB, ed. (2016). Guidelines for the Primary and Gender-Affirming Care of Transgender and Gender Nonbinary People. UCSF Transgender Care. https://transcare.ucsf.edu/guidelines
Nolan BJ, et al. (2020). Progesterone for trans women: a clinical review. Journal of the Endocrine Society.