Prognostic signs in the evolution of premature thelarche by discriminant analysis

Abstract

Since premature thelarche (PT) can be a first sign of precocious puberty (PP), the aim of our study was to identify simple items in the course of the first 6 months of follow-up that could help predict if PT would evolve to PP. Thirty-two girls with PT were studied. First evaluation included bone age (BA), basal estradiol, FSH, LH and prolactin. GnRH was performed in 15 subjects and BA was checked at 6 month intervals in 30. Based on clinical outcome after a mean follow-up of 33.4 ± 16.5 (SD) months, patients were divided into 2 groups: Group I (G-I) included subjects whose breast development either remained unchanged, increased or regressed; Group II (G-II) included subjects who progressed to PP. The multivariate combination of the items which was able to best discriminate between the two groups was chosen in predicting the evolution of PT. The items considered included four variables available at the time of diagnosis [chronological (CA) at onset <3 years, basal FSH, basal LH and BA/CA ratio] and two additional variables after a 6-month follow-up (ΔBA/ΔCA and growth velocity); 88% of G-I and 14% of G-II had CA <3 yr. Basal FSH levels were elevated in both G-I (7.6 ± 3.0 mill/ml) and G-II (12.1 ± 4.1) with respect to controls (2.6 ± 1.2); however, approximately 20% of G-I had low FSH levels. Basal LH levels were consistently higher in G-II (8.0 ± 1.3 mlU/ml) than in G-I (2.9 ± 1.5) or controls (2.8 ± 1.2). Although initial BA was advanced (>2SD) in 21% of G-I and in all of G-II, an acceleration of BA was seen only in G-II. The mean growth velocity of G-I (44.1 ± 31.5%) was significantly less than G-II (92 ± 32%; p < 0.0025). With the help of the discriminant equations derived from data obtained at diagnosis and during the first 6 months of follow-up, all subjects with isolated premature thelarche could be sharply distinguished from those who subsequently progressed to precocious puberty. Such an equation should help in predicting the probability of considering either a diagnosis of isolated premature thelarche or precocious puberty in a child who presents with precocious breast development.