OBJECTIVETo investigate the efficacy of letrozole for delaying bone maturation and increasing predicted adult height in boys with idiopathic central precocious puberty (ICPP) who have a bone age above 13 years and a short stature, and its adverse effects.

METHODSTwenty ICPP boys with a bone age above 13 years and a short stature were randomly divided into letrozole treatment (n=10) and control groups (n=10). The letrozole treatment group received oral letrozole [2.5 mg/(m(2)·d), Qd] for 6 months, while the control group received no treatment and was observed periodically. Bone age, growth rate, height standard deviation (SD) score, predicted adult height SD score, sexual maturity, and levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), dehydroepiandrosterone, testosterone (T), estradiol (E2), progesterone (P), and androstenedione (ASD) were measured. The letrozole-related adverse reactions were evaluated.

RESULTSAfter 6 months of treatment, both groups had a significantly increased bone age, but the letrozole group had a significantly slowed increase in bone age compared with the control group (13.82 ± 0.23 years vs 14.47 ± 0.30 years; P<0.05); compared with the control group, the letrozole group had a significantly increased predicted adult height SD score (-1.69 ± 0.26 vs -1.91 ± 0.35; P<0.05) and a significantly increased T level (4.9 ± 0.9 nmol/L vs 4.4 ± 0.8 nmol/L; P<0.05). There was no significant difference in testicular volume between the two groups. The treatment led to no significant changes in growth rate, Tanner stage, and levels of FSH, LH, P, E2 and ASD in the two groups, and there was no significant difference in these indices between the two groups. No adverse reactions were observed during letrozole treatment.

CONCLUSIONSLetrozole delays bone maturation and increases predicted adult height in ICPP boys with a bone age above 13 years and a short stature, and it causes no obvious adverse reactions.