What is the common cause of premature thelarche in girls?

Premature thelarche, the early development of breast tissue in young girls, is primarily caused by ovarian estrogen production. During this stage, the ovaries may start to produce estrogen in a manner similar to the hormonal changes seen during normal puberty, albeit at an earlier age. This estrogen leads to the development of breast tissue before the age of 8, which is considered premature.

While adrenal androgen production and hypothalamic stimulation can play a role in other conditions related to early sexual development or disorders of puberty, they are not the most common causes of premature thelarche. Similarly, genetic predisposition can influence overall timing and development of puberty, but it does not directly account for the hormonal changes that lead to early breast development. Therefore, ovarian estrogen production is recognized as the primary factor in the occurrence of premature thelarche in girls.