Estradiol Cypionate
Longer-acting injectable estradiol ester. The cypionate ester releases estradiol more slowly than valerate, allowing longer dosing intervals; used in feminizing HRT and formerly in monthly combined injectable contraceptives.
01 Overview
Estradiol cypionate is a fatty-acid ester prodrug of 17-beta-estradiol with a longer release profile than estradiol valerate, so it can be dosed every 1-2 weeks. It sees widespread use in transfeminine hormone therapy and was a component of the monthly contraceptive Cyclofem/Lunelle.
As with all injectable estrogens, monitoring targets a physiologic serum estradiol range. The slower release can make level-chasing smoother but also makes overshoot slower to correct.
02 Mechanism
Cypionate ester is cleaved to 17-beta-estradiol, which activates estrogen receptors to drive feminization and suppress gonadotropin output.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Feminizing HRT | 2–5 mg/wk | IM | Often given as 2-5 mg every 1-2 weeks; titrate to serum estradiol. |
| Feminizing HRT (SC) | 2–5 mg/wk | SubQ | SC route used off-label with comparable exposure. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| FeminizationBreast growth, fat redistribution and skin softening as with other estradiol forms. | Clinical | ||
| Stable estradiol levelsLonger ester reduces peak-trough swings versus shorter esters for some users. | Observational |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Thromboembolic riskEstrogen therapy raises VTE risk; magnitude scales with dose, age and smoking. | Severe | Uncommon | Clinical | |
| Mood labilityMood changes during initiation or with fluctuating levels. | Mild | Common | Observational |