OBJECTIVETo investigate the clinical status and natural course of premature thelarche (PT) in infants under 2 years of age and to analyze the predictive factors for regression of thelarche.

METHODSThe clinical and laboratory data of 863 infants under 2 years of age, who visited the department of endocrinology in our hospital due to PT between October 2009 and September 2010, were analyzed. A a longitudinal follow-up study was performed.

RESULTSOf the infants under 2 years of age with isolated PT, 89.3% showed a regression before the age of 3 years (mean 17±5.6 months), 10.7% had recurrent or persistent thelarche, with no regression after the age of 3 years, and some even developed into central precocious puberty. The independent predictive factors for regression of thelarche were Tanner stage at the first visit and whether baseline estradiol level had increased.

CONCLUSIONSPT in infants under 2 years of age is not rare in the clinical setting, and it usually runs a self-limited course, subsiding before the age of 3 years. However, regular follow-ups should be performed for infants aged over 2 years with persistent thelarche.