OBJECTIVEGonadotropin-releasing hormone agonist (GnRHa) is widely used for the treatment of precocious puberty, but there was no identical regime for the dosage and the interval of administration. The aim of this study was to assess the feasibility of subcutaneous administration of Triptorelin with a prolonged interval (six weeks) for the suppression of pituitary-gonadal axis and clinical signs in girls with idiopathic central precocious puberty (ICPP).

METHODSForty-six girls with ICPP were enrolled in this trial and were divided into two groups at random, with 26 patients in group A and 20 in group B. There were no significantly differences in chronological age, height, weight, age at clinical onset of puberty and bone age between the two groups before treatment. Triptorelin (Decapeptyl, 3.75 mg) was administered subcutaneously (SC) at 6 weeks intervals in group A or intramuscularly (IM) at 4 weeks intervals in group B. Both forms were given for more than 12 months consecutively. During the period of treatment, the clinical parameters including height, weight, pubertal stage, bone age, uterine volume and ovarian size were documented. The serum levels of luteinizing hormone (LH), follicle stimulating hormone (FSH) and estradiol (E(2)) were monitored using immunoenzymometric assay.

RESULTSBoth treatment regimes can completely suppressed the pituitary-gonadal axis. The clinical signs of pubertal development regressed or stabilized in all patients. Breast developments, as reflected by Tanner staging, were regressed. Uterine volume decreased after treatment, however, this decrease did not reach statistical significance. Mean ovarian volume did not change significantly during treatment. The height velocity was significantly decreased from a pretreatment value of 6.3 +/- 1.4 cm/year to 5.8 +/- 1.2 cm/year in group A and 6.7 +/- 1.3 cm/year to 5.4 +/- 1.0 cm/year in group B, respectively. The rate of skeletal maturation was reduced significantly during treatment. The ratio of bone age/chronological age was 1.2 +/- 0.2 or 1.3 +/- 0.3 at the onset of therapy and decreased significantly after the treatment to 0.7 +/- 0.2 or 0.9 +/- 0.1, respectively. The predicted adult height increased significantly and progressively during therapy. The levels of serum LH, FSH and E(2) were returned to the prepubertal condition after 6 - 8 weeks treatment and remained suppressed for the duration of treatment. No significantly side effects of therapy were noted. The most common adverse event during SC treatment was that a non-irritating, 1 cm in diameter mass can be palpated at the site of subcutaneous injection in the abdominal wall of group A patients. It gradually decreased in size, and disappeared after 8 - 12 weeks. Two girls had minimal withdrawal virginal bleeding episodes after the first injection.

CONCLUSIONBoth IM and SC triptorelin administration were clinically effective. They can induce profound suppression of hypothalamic-pituitary-gonadal axis while stabilizing height velocity, slowing bone maturation and increasing predicted adult height. These results suggest that subcutaneous injection of triptorelin in 6 weeks intervals at a dosage of 3.75 mg was a safe and acceptable regime for ICPP with good efficacy.