Breast growth during the first year of HRT: what can I expect?

Posted on January 31, 2019 by Aaricia

For many transgender individuals looking to see breast growth, the main question is: “How much breast development can I expect on HRT, and when will it start?”. Let’s take a look at breast development during the first year on anti-androgens and estrogen.

This article is describes the findings of the first scientific study on breast development after HRT in trans women (Breast Development in Transwomen After 1 Year of Cross-Sex Hormone Therapy: Results of a Prospective Multicenter Study (2017)– Christel Josefa Maria de Blok en co-authors)

This detailed study was performed on 229 trans women who completed their first year of Hormone Replacement Therapy. Their ages ranged from 18 to 69, the median age being 28 years at the start of the study.

What to expect: breast growth after one year on HRT

What to expect: breast growth after one year on HRT

When will my breasts start growing after starting on HRT?

Breast development mostly occurred during the first 6 months on Hormone Replacement Therapy. The average increase over the first 3 months being 1.8 cm, and another 1.3 cm over the following 3 months. During the last 6 months, the average total growth was only 0.5 cm. It can hereby be concluded that main breast growth takes place in the first six months of HRT.

How much breast development can I expect on HRT?

After one year of HRT, the average increase in breast growth was 3.8 cm. When translating this to bra cup size, this meant around 50% of all participating women had less than an AAA cup after one year. Less than 5% of all women gained a cup size larger than an A cup.

More follow-up research is needed to be able to accurately predict breast growth in the following year(s) of HRT.

Do factors like smoking, BMI, weight change, age,… influence breast development?

The short answer is: no.

In the study:

  • Breast growth does not vary in different age groups.
  • Breast growth does not vary based on weight change, weight gain or weight loss.
  • Obese trans women showed faster growth in the first months of HRT, but total breast-chest difference after 12 months was the same in normal weight, overweight and obese trans women.
  • Breast growth does not vary in smokers versus non-smokers.
  • Breast growth had a faster increase in trans women treated with transdermal estradiol for the first six months, but total breast development after one year saw no difference between the intake of oral or transdermal estradiol.


So we can conclude that the current study shows a modest increase in breast-chest difference after 1 year of CHT, mainly resulting in less than an AAA bra cup size. Age, weight change, smoking, BMI, serum estradiol levels, and estrogen administration route did not predict total breast development after 1 year of CHT.

Because of the modest results of HRT on breast development, many trans women seek to get a breast augmentation. It is advised to wait with surgery until you have been on HRT for 18 months.



Can I start HRT with you in Belgium? The waiting lists in my country are so long

Yes, you are welcome at 2pass Clinic for your HRT treatment. You can make your appointment here.

Important: You need a letter of approval from your therapist before you can start hormone treatment. You can get this approval at 2pass Clinic as well, by making an appointment with our psychologist.

How often should I make an appointment if I start with my hormone treatment at 2pass Clinic?

In the first year there are quarterly check-ups by the endocrinologist; in the second year of hormone treatment, every six months. An annual follow-up is often carried out after gender-confirming operations.

What are the waiting times? How long after my first visit to the endocrinologist before I can start HRT?

There barely are waiting times. A few weeks at the very most.

Once you’ve had your first appointment, usually you will be able to start with HRT two weeks later. Once the blood results are in and once they have been discussed with the endocrinologist. You can book your appointment here.

How long will it be until I see the development of my breasts?

In general, you will start to notice breast development between three and six months after starting with HRT. After two years they will have reached their maximum natural size. However, in some people there may not be any growth at all. Read more about the effects of HRT on the MtF body.

When does fat redistribution start when taking HRT?

You will be able to really start noticing changes from about 6 months onward after having started HRT. In some people it may take longer before they start seeing changes.

Should I wait with FFS until I have taken hormones long enough?

The hormones will have their effect on the soft tissues of your face: the fat will redistribute and the muscles will atrophy a bit. Also the facial hair will diminish and hair to the scalp will become denser and thicker. All this will make your face look softer and more feminine.
Dr van de Ven will try to make your face as feminine as possible and there is no negative effect to your face becoming even more feminine after your FFS due to the hormones. Those last changes will be very subtle. Therefore Dr van de Ven does not see a reason to postpone FFS if you have only started taking hormones recently.

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