Hormonal breast enhancement

Estradiol by itself doesn't stimulate breast development. IGF-1 acts in concert with estradiol to build breast tissue and determine final breast size. In essence, estradiol pulls the steering wheel towards "breasts", and IGF-1 slams the gas pedal. In fact, IGF-1 is the strongest determinant of breast size as measured during the follicular phase of cisgender women.

Risks of increasing IGF-1
Acromegaly, a masculinizing pronouncement of facial bone structure, is caused by abnormally high levels of IGF-1.

IGF-1 has been linked to breast cancer.

Naturally increasing IGF-1

 * Supplementing Vitamin D3 increases IGF-1.
 * Sleeping well.
 * Exercise.
 * Gaining weight.

Artificially increasing IGF-1

 * Mk-677 amplifies the production of IGF-1, rather than simply increasing production by a constant level. This means that the body's natural cycle of IGF-1 production will only be heightened, with higher peaks. This drug has been under clinical investigation for some time, however its primary use is bodybuilders.