Factors predicting adult height in girls with idiopathic central precocious puberty: implications for treatment.

OBJECTIVES: To optimize the indications for treating girls with idiopathic central precocious puberty with GnRH analogues, since outcomes may vary.

DESIGN: Comparison of adult heights with the data at initial evaluation and the target heights.

PATIENTS: Group 1 patients (n = 43) were treated with GnRH analogue from 7.9 +/- 0.2 years to 10.8 +/- 0.1 years (bone age: 10.3 +/- 0.2 years to 12.2 +/- 0.1 years) and group 2 patients (n = 29) were monitored without treatment because their predicted adult heights were > 155 cm. The criteria for treatment were a predicted height < 155 cm and/or a LH/FSH peaks ratio of > 0.6.

RESULTS: At initial evaluation, group 1 patients had greater breast development (P = 0.001) and bone age advances (2.0 +/- 0.2 years) than those of group 2 (1.3 +/- 0.2 years, P < 0.3), and higher plasma oestradiol concentrations (139 +/- 11 pmol/l vs. 62 +/- 7 pmol/l, P = 0.0001), LH peak (12.2 +/- 1.8 IU/l vs. 5.8 +/- 2.2 IU/l, P = 0.0001) and LH/FSH peaks ratio (1.3 +/- 0.2 vs. 0.5 +/- 0.1, P = 0.0001). The predicted height for group 1 at the onset of treatment (156 +/- 1.2 cm) was lower than the adult height (159.5 +/- 0.8 cm, P = 0.002), but the two were similar (164.1 +/- 1.2 cm vs. 162.7 +/- 0.9 cm) for group 2. In group 1, the difference between these heights (mean 3.4 cm) was positively correlated with the bone age advance (r = 0.51, P = 0.001), but not with chronological or bone ages, oestradiol, LH peak, LH/FSH peaks ratio before treatment or its duration. It was 5.3 +/- 1.2 cm in the 28 patients with a bone age advance of > 2 years and 0 +/- 1.3 cm in the other 15 (P < 0.02). It was 6.1 +/- 1.3 cm in the 24 patients with predicted height < 155 cm, and -0.1 +/- 1.1 cm in the other 18 (P = 0.002). The 72 patients included nine who attained an adult height over 5 cm shorter than the target height (seven treated and two untreated). The seven treated subjects included two who had retarded intrauterine growth.

CONCLUSIONS: Treatment of girls with idiopathic central precocious puberty with GnRH analogues produced a mean height increase of 3.4 cm between the predicted and adult heights. The increase was greater for girls with a bone age advance of > 2 years and a predicted height < 155 cm. Adult height is spontaneously preserved in the slowly progressing form. The classical and slowly progressing forms can be distinguished by the degrees of breast development and bone age advance.