There exists also substantial variation in dimensions amongst persons. Long term breast advancement all through puberty is caused by estrogens together with The expansion hormone. Female people are the only mammals that permanently develop breasts at puberty; all other mammals establish their mammary tissue over the latter period of pregnancy. https://grok.com/share/c2hhcmQtMw%3D%3D_5ad6450c-533d-442c-a09c-9f7bce1babfb