Relationship between prolactin level and puberty in girls with early breast development.

OBJECTIVES: Prolactin (PRL) stimulates the mammary glands development; however, it also inhibits gonadotropin-releasing hormone (GnRH) secretion. We evaluated the relationship between PRL levels and puberty in girls with precocious breast development.

METHODS: This study included 244 girls with breast development < 8 years of age. Patients were categorized as central precocious puberty (CPP) [peak luteinizing hormone (LH) levels ≥ 5 IU/L after GnRH stimulation] versus non-CPP (NPP) group. High PRL was defined as serum PRL > 17.9 ng/mL.

RESULTS: High PRL was more common in NPP than in CPP group (17.6 vs. 8.1%, p=0.025), although mean PRL levels did not differ. In NPP group, the high PRL group had lower peak LH/follicle-stimulating hormone (FSH) ratio, and later LH peak time after GnRH stimulation than normal PRL group (all p < 0.05). PRL levels of the subgroups according to the peak LH time (15, 30, 45, 60, and 90 min after GnRH stimulation) were different in NPP group, but not in CPP group. PRL levels tended to be higher as the peak LH time was delayed. High PRL was associated with decreased odds for CPP (OR=0.42, p=0.043).

CONCLUSIONS: Girls with NPP showed higher proportion of high PRL than CPP group. High PRL group showed more features of prepubertal response in NPP group, and associated with decreased odds for CPP, suggesting the possibility of PRL role on breast development while suppressing hypothalamic-pituitary-gonadal axis activation in NPP girls.