Premature thelarche in later childhood demonstrates a pubertal response to GnRH stimulation test at one year after breast development.

Premature thelarche in later childhood (such as at 5-7 yr of age) is not always easy to distinguish from GnRH-dependent precocious puberty. In this study, a GnRH stimulation test was performed on 21 girls from 5 to 7.5 yr of age with early breast development. In 8 of 11 girls within 1 yr after thelarche, i.e., breast development, the GnRH stimulation test showed a prepubertal response, and in all 10 girls at more than 1 yr after breast development, the GnRH stimulation test showed a pubertal response. In observations of 4 girls with a prepubertal response, the GnRH stimulation test showed to a pubertal response by 1 yr or more after breast development in 3 of 4 the girls. These results indicate the possibility that almost all cases of breast development in later childhood consist of premature thelarche and that premature thelarche in later childhood may easily lead to early puberty at 1 yr or more after breast development. Careful observations are therefore recommended for at least 1 yr, even if early breast development is considered to be associated with premature thelarche in later childhood.