Evidence for increased ovarian follicular activity in girls with premature thelarche.

Objective: Inhibin B is produced by granulosa cells in small antral follicles, under the influence of FSH, and has a paracrine role in oestradiol synthesis. To test the hypothesis that premature thelarche is associated with increased FSH-driven follicular development, we measured inhibin B and FSH in girls with premature thelarche, girls with central precocious puberty (CPP) and controls matched either for age or breast stage.

Patients: Blood samples were collected from 11 girls with premature thelarche (breast stage 2, aged 0.4-5.6 years), 11 prepubertal controls age-matched to the thelarche girls (0.5-5.4 years), 13 girls with CPP (breast stage 2, 3.9-8.2 years) and nine normal pubertal controls (breast stage 2, 9.0-13.2 years).

Measurements: Dimeric inhibin B was measured in plasma by double-antibody enzyme-linked immunoassay and FSH by immunoradiometric assay. Pelvic ultrasonography was performed on all girls with CPP and 10/11 girls with premature thelarche.

Results: Seven of the 13 girls with CPP and three of the eight girls with premature thelarche whose ovaries could be visualized had visibly nonhomogeneous ovarian structure on ultrasonography. Girls with premature thelarche had inhibin B and FSH concentrations higher than those in their age-matched controls (P < 0.01 and P < 0.05, respectively), and similar to those observed in girls with CPP and normal pubertal controls matched for breast stage. In thelarche girls, as in precocious puberty girls and normal pubertal controls, inhibin B and FSH were positively related (rs = 0.54-0.61).

Conclusions: This study provides further evidence that premature thelarche is associated with enhanced follicular development, similar to that which occurs in early puberty, probably under the influence of FSH.