Context and objective: Girls with precocious pubarche (PP, pubic hair at < 8 yr of age) are at high risk for early onset and rapid progression of puberty, in particular if their prenatal growth was restrained, i.e. low birth weight (LBW), and followed by rapid postnatal catch-up of weight gain. We postulated that insulin resistance contributes to early onset and rapid progression of puberty in LBW-PP girls and thus explored the puberty-delaying effects of insulin sensitization with metformin initiated shortly after PP diagnosis.
Setting, design, and patients: The study population consisted of 38 prepubertal LBW girls with PP attributed to exaggerated adrenarche [mean body weight, 2.4 kg; age, 7.9 yr; body mass index (BMI), 18.4 kg/m(2)]. These girls were randomly assigned to remain untreated (n = 19) or to receive metformin (n = 19; 425 mg/d) for 2 yr.
Main outcome measures: Pubertal staging, age at menarche, body composition by absorptiometry, fasting insulin, glucose, lipids, leptin, IGF-I, IGF-binding protein-1, testosterone, dehydroepiandrosterone sulfate, and SHBG were the main outcome measures.
Results: Metformin treatment was associated with a less adipose body composition (and lower serum leptin levels) and with a 0.4-yr delay in the clinical onset of puberty (Tanner B2; 9.5 vs. 9.1 yr; P < 0.01). These findings were corroborated by a delay of at least 1 yr in the puberty-associated rise of circulating IGF-I (P < 0.01). Available results also point to a metformin-associated delay of menarche (P < 0.02). Gain in height and lean mass was not divergent between study subgroups.
Conclusion: The efficacy of early metformin treatment in PP girls is here extended to include not only a less adipose body composition after 2 yr but also a less advanced onset of puberty, whereas height gain is maintained. These findings open the perspective that, ultimately, metformin treatment may also prove to heighten the short adult stature of LBW-PP girls.