Hormone therapy is not necessary for M-F transgender breast augmentation, but if you are unsure about HRT (hormone replacement therapy), or if you have just started it, you need to understand that female hormones (and testosterone-inhibiting medications) will cause changes in your breasts, muscles, and fatty tissues, all of which impact results of breast augmentation.
When a trans woman is taking hormones, most plastic surgeons experienced in surgery for transgender patients will recommend waiting at least 18 months for maximum changes in the breasts to be seen. This time period also corresponds with WPATH guidelines, which may need to be adhered to if insurance reimbursement is being sought. In my experience, most insurance plans do not cover breast augmentation, even in trans women, but the physiologic effects and time recommendations are still appropriate to follow.
Many of my M-F transgender patients have decided for one reason or another that they will not be taking female hormones, and breast augmentation is perfectly fine to consider whenever they decide to proceed.
But if you are considering HRT, or have just started it, you would be wise to allow your breasts to achieve whatever growth hormones may stimulate for a full 18 months or more, and not ask your plastic surgeon to try to "hit a moving target" and still give you the results you desire and deserve! Best wishes! Dr. Tholen