Breast enlargement in girls under eight years of age is relatively common and self-limited (Fig. 13.39). Premature thelarche most frequently occurs in girls by two years of age and almost always before four years of age. In most cases, the breast development will regress within six months of onset, but in some cases remains for years after diagnosis. Long-term follow-up suggests that no untoward effects occur on later health. The cause of premature thelarche may be the development of a small ovarian cyst, but usually by the time the outward physical manifestations are noted, the cyst has regressed and no laboratory tests are indicated. Studies have shown elevation of FSH levels to be a potential cause of premature thelarche, but patients do not manifest a true pubertal GnRH test. This is a benign self-limited disorder and should be treated with reassurance.
