MON-242 - Natural Course of Premature Thelarche in Infants Under Two Years: A Follow-Up Study on Predictive Factors for Differentiating Central Precocious Puberty and Premature Thelarche

Objective: Premature thelarche (PT) is characterized by the development of unilateral or bilateral breast tissue before the age of 8, without other secondary sexual characteristics, and is most commonly observed before 2 years of age. PT occurring after 3 years of age is more likely to be associated with causes other than benign premature thelarche. Although PT is generally a benign condition, it may represent the initial manifestation of central or peripheral precocious puberty, making differentiation between these conditions challenging and necessitating close monitoring. This study aimed to investigate the natural course of premature thelarche in infants under 2 years of age and identify predictive factors that distinguish central precocious puberty (CPP) from premature thelarche (PT).

Methods: This study included 102 female infants under 2 years of age who presented with premature thelarche at a single tertiary pediatric endocrinology outpatient clinic between January 2010 and August 2022, and were followed up for more than one year. We compared chronological age, bone age, height, weight, breast development stage, luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol (E2), thyroid-stimulating hormone (TSH), and changes in breast development stage between the CPP and PT groups.

Results: Among the 102 infants followed for more than one year, breast development progressed in 6 (6.3%), regressed in 31 (32.6%), and remained stable in 58 (61.1%) cases. All cases of regression were observed in the PT group, while 10 (17.2%) of those with stable breast development were diagnosed with CPP, compared to 48 (82.8%) in the PT group (p=0.019). A total of 19 infants were diagnosed with CPP, while 83 were classified as PT. There were no significant differences in height, weight SDS, or initial breast development stage between the two groups. Baseline FSH, E2, and TSH levels also did not differ significantly. However, baseline LH levels were significantly higher in the CPP group (0.579 IU/L) compared to the PT group (0.280 IU/L) (p < 0.05). The initial bone age to chronological age ratio was also significantly higher in the CPP group (1.64) than in the PT group (1.38), and this difference persisted after more than one year of follow-up (CPP: 1.46, PT: 1.20) (p < 0.05).

Conclusion: In female infants under 2 years presenting with breast development, it is crucial to differentiate between premature thelarche and precocious puberty. This differentiation requires an initial assessment of baseline LH levels and bone age. Regular follow-up monitoring of changes in the bone age to chronological age ratio and breast development is essential for early identification of central precocious puberty.

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