Estrogen HRT & Breast Growth

Have you wondered how estrogen HRT changes your body? There isn’t a ton of clinical data looking at the effects of estrogen on breast growth, especially for trans, non-binary, and GNC folks, but in this article we look at what we do know, what size most people will arrive at, and what you can do if all the changes are happening a bit too fast.

February 1, 2023
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People who start estrogen hormone replacement therapy will notice many changes in their body and breast growth is one of the earliest and most noticeable developments. This increase in chest tissue (medically called gynecomastia) happens between two to six months after someone begins taking estrogen and is one of the  irreversible changes for estrogen  HRT. Most people, if not all, will undergo breast development, but the degree and size to which their chest grows varies widely and is dependent on multiple factors. 

One of the most common questions that our clinicians here at FOLX get is, “How big will my chest get?” This is a common question for anyone embarking on a new unknown journey of gender affirmation.. To shed more light on the process of breast growth through estrogen HRT, we consulted Samantha Hyacinth, our resident nurse practitioner, about what changes you can expect to see and when. 

What kind of breast growth can I expect when on estrogen HRT? 

“It’s important to know that all chest tissue is the same regardless of someone’s assigned gender at birth,” says Samantha. When that tissue is exposed to estrogen, whether because of natal hormones or through medication, it responds in the same way: it grows.

The first thing someone will typically notice is tenderness of the entire chest or in the nipple and areola area. After that point, some people may start to notice swelling in addition to the sensitivity. This can be sore or uncomfortable, but eventually leads to developing breast buds, which are hard pea-sized lumps right beneath the nipple, from where the actual breast starts to grow.

Is there a way to gauge how big my breasts are going to get while taking estrogen?

It’s hard to predict how much your breasts will develop while taking estrogen because there are multiple factors at play. The dosage of hormones you’re on, if you’re also taking an anti-androgen like spironolactone, race, and genetics (as always) all play a role in the process of breast growth. How much fatty tissue someone has on their body and where they carry it is also a factor to consider since fat is a major component of breast biology. 

“The best way to predict your breast size is to look at people in your family who were assigned female at birth,” Samantha recommends. 

Clinical research on this topic—like most other areas of transgender health—is minimal. Most recently, a European team of researchers followed 229 transgender woman on HRT for a year and observed their breast growth, making this one of the more extensive studies on estrogen HRT and physical changes. They found that over 90% of participants developed breasts in the A-cup range regardless of oral or transdermal estrogen route. 

Is breast growth different if I’m just taking estrogen without an anti-androgen

Estrogen on it’s own induces breast development, and anti-androgens like spironolactone have a side effect of growth of chest tissue. Theoretically, people taking estrogen and spiro as part of their HRT routine could get an extra boost in breast development, but it’s hard to say. Spironolactone also isn’t exclusive to gender-affirming therapy and is often prescribed for blood pressure or acne. People who take spiro for any reason are susceptible to the same side effects like lightheadedness, increased frequency of urination, and breast enlargement. 

Unsurprisingly, there aren’t any substantial studies that compare breast growth in people just taking estrogen compared to those taking estrogen and an anti-androgen. And we know that it’s hard to make a broad generalization for a community with such diverse bodies and genetics.

What will my body look like after three months on estrogen? Six months? A year?

There are physical change timelines from the medical community that show when specific changes might happen, for how long they’ll last, and when they’ll peak in effect. This can give you a general idea of how your body will develop over the course of months and years of taking estrogen. Breast tissue growth is one of the earliest changes to take shape in your body starting from two to six months into estrogen HRT. The specificity of these changes depend on many factors. 

“Comparing those tables to what people actually tell me doesn’t always match, as it typically is when comparing textbooks to actual people,” says Samantha.

an illustration of breast growth on estrogen pre, low does and high dose

My body is changing too fast. What can I do?

It’s important to remember that you’re in control of your gender journey with HRT and that doesn’t have to look linear. “More people need to know that they can pause hormones just to think and process and be in your body,” says Samantha. Luckily for those who are looking to move through this journey one baby step at a time, most of the physical changes tend to move forward gradually. Decreasing your dosage of hormones will also slow down the development and pace of transitioning, and you can always revisit hormones if and when you feel ready. 

If you'd like to get started on estrogen GAHT with FOLX, sign up here.


FOLX Health is the first digital healthcare company designed by and for the LGBTQIA+ community. Our services include virtual primary care, gender-affirming hormone therapy including estrogen and testosterone (HRT), mental health care, sexual and reproductive health care, preventive care, and fertility consultations. FOLX memberships give you access to LGBTQIA+ expert clinicians, peer support, thousands of LGBTQIA+ resources, and more. Whether you’re lesbian, gay, bisexual, transgender, queer, gender non-conforming, or nonbinary, you can find LGBTQIA+-specialized health care that helps you meet your wellness goals. FOLX Health is health care that's queer all year. Get all the benefits of becoming a FOLX member and sign up today!