Has a 10-year-old girl already started developing if her breasts have begun to enlarge? Is this normal?

Generally speaking, it is usually a normal developmental phenomenon for a 10-year-old girl's breasts to enlarge. The detailed explanation is as follows:

In most cases, girls begin breast development between the ages of 9 and 11, indicating the onset of puberty and the beginning of secondary sexual characteristic development. Therefore, breast development and gradual enlargement in a 10-year-old girl is considered normal. At this time, girls may also exhibit other characteristics such as a higher-pitched and thinner voice, increased subcutaneous fat, and gradual increases in weight and height. However, it should be noted that if the breast development progresses too quickly or becomes excessively large beyond the normal range, it may be related to endocrine disorders. Additionally, if a girl suffers from endocrine disorders such as hyperthyroidism or polycystic ovary syndrome, she may also experience significant breast development. In such cases, timely medical consultation and treatment under a doctor's guidance are necessary.

Parents are advised to pay attention to the girl's growth and development, encourage a healthy lifestyle, and avoid staying up late, all of which contribute to healthy growth.