Development of antibodies against growth hormone (GH) during rhGH therapy in a girl with idiopathic GH deficiency: a case report.

A 12.5-year-old Italian girl was referred to our institute for progressive growth failure from the age of 6 years, with a height of 128.2 cm (-3.37 SDS) and a bone age of 9 years. Endocrinological evaluation revealed a partial growth hormone deficiency (GHD) and GH therapy was started at a dosage of 0.25 mg/kg/week. During the first 3 years, she showed an increase in growth rate and experienced pubertal development onset. Then a poor growth rate (2 cm/year=0.43 SDS) was observed, notwithstanding an increase in GH dosage (0.35 mg/kg/week) and good compliance. We found a positive anti-GH antibody titre (1:1850, cutoff 1/100), confirmed 6 months later (1:2035); the antibodies had low binding capacity (0.63 μg/mL) and were only partially capable of inhibiting the GH effect. However, GH treatment was discontinued, and after 3 months the antibody titre decreased (1:950). In conclusion, we suggest evaluation of anti-GH antibodies in GH-treated idiopathic GHD children in whom growth response decreases after some years of therapy.