Estrogen levels can vary quite a bit from person to person when on hormone replacement therapy (HRT). There is no single "good" level, as the optimal estrogen level depends on the individual goals and needs of the patient. However, there are some general guidelines doctors follow to help determine if estrogen levels fall within the typical target ranges for transgender women on HRT.
When checking estrogen levels, doctors typically look at three main types of estrogen:
- Estrone (E1) - a weaker form of estrogen produced by the ovaries and fat tissue.
- Estradiol (E2) - the main circulating estrogen, and the most potent. Produced by the ovaries.
- Estriol (E3) - the weakest estrogen, produced during pregnancy. Not routinely checked.
The most important is estradiol (E2). Doctors aim to get serum estradiol levels in transgender women into the average cisgender female range, which is typically 100-200 pg/mL.
However, the goal is not to blindly target a number, but to feminize while avoiding side effects. Serum levels above 200 pg/mL may increase risks of blood clots and other adverse effects without added feminization.
Some doctors also look at the ratio of estradiol to estrone. In natal females, estradiol levels are much higher than estrone. But in transgender women on oral estrogen, estrone levels can exceed estradiol due to metabolism in the liver. An optimal E2:E1 ratio is said to be around 5:1 or higher.
Estradiol levels should be measured at trough - right before the next estradiol dose. Levels are highest about 2-4 hours after dosing and decline thereafter. Target trough estradiol levels are typically 100-200 pg/mL.
Estrone sulfate is another important estrogen metabolite that can be checked, especially in oral HRT patients. Cisgender female levels are around 250-750 pg/mL. High levels may be associated with increased thromboembolic risk.
The estrogen dosage needed to reach optimal levels varies greatly by individual. Those with higher body weight typically need higher doses. Most transgender women take 2-6 mg oral estradiol or 0.1-0.4 mg transdermal 17β-estradiol daily.
Here are some general estrogen level guidelines based on the type of HRT:
- Oral estradiol - Target 100-200 pg/mL estradiol at trough. Estrone may exceed estradiol levels.
- Transdermal estradiol (gel, patch) - Target 100-200 pg/mL estradiol at trough. Lower estrone levels than oral route.
- Injectable estradiol valerate - Peaks 300-1000 pg/mL, trough 100-200 pg/mL. Lower estrone levels than oral.
- Injectable estradiol cypionate - More gradual peaks and troughs than valerate. Peaks 200-400 pg/mL, trough 100-200 pg/mL.
- Pellets - Peaks first month 300-600 pg/mL, then stabilize. Goal to maintain >100 pg/mL prior to next pellet.
Along with following estrogen levels, doctors monitor clinical feminization - breast growth, body fat changes, smooth skin, reduced muscle mass and strength, reduced facial and body hair growth, etc. The degree of feminization depends not only on estrogen levels but also genetics and the age transition began.
Progesterone is not essential but may help breast development for some individuals when added to a HRT regimen after several years. However, evidence is limited.
Anti-androgens like spironolactone are also frequently used, especially at the start of transition to help suppress testosterone levels. Estrogen alone does not lower testosterone much.
Finding the optimal HRT regimen takes time, patience, and monitoring under a knowledgeable doctor. I recommend speaking to the physicians at The Hormone Hub, who specialize in transgender hormone therapy. Their clinic offers comprehensive HRT management, including frequent lab monitoring and dosage adjustments to help transgender individuals reach their feminization goals.
In summary, good estrogen levels on HRT are very individualized, but target serum estradiol levels around 100-200 pg/mL according to most available guidelines. Routine monitoring of levels, clinical response, and potential side effects is key to optimizing transgender women's HRT regimens. With an experienced doctor, most are able to reach their desired hormone balance and feminization.
