DOI 10.1515/jpem-2013-0064 J Pediatr Endocr Met 2013; aop Patient report Cristina Meazza, Michael Schaab, Sara Pagani, Valeria Calcaterra, Elena Bozzola, Juergen Kratzsch and Mauro Bozzola* Development of antibodies against growth hormone (GH) during rhGH therapy in a girl with idiopathic GH deficiency: a case report Abstract: 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 ther- apy 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. Keywords: anti-GH antibodies; growth hormone (GH) deficiency; growth hormone (GH) therapy. *Corresponding author: Mauro Bozzola, MD, Department of Internal Medicine and Therapeutics, University of Pavia, Fondazione IRCCS Policlinico San Matteo Piazzale C. Golgi 2, 27100 Pavia, Italy, Phone: +39 0382 502891, Fax: +39 0382 502876, E-mail: mauro. bozzola@unipv.it Cristina Meazza, Sara Pagani and Valeria Calcaterra: Department of Internal Medicine and Therapeutics, University of Pavia, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy Michael Schaab and Juergen Kratzsch: Institute of Laboratory Medicine, Clinical Chemistry and Molecular Diagnostics, University of Leipzig, Leipzig, Germany Elena Bozzola: Pediatric and Infectious Disease Unit, Department of Pediatrics, Bambino Gesù Children’s Hospital, Rome, Italy Introduction Since the 1980s, recombinant human GH (rhGH) has been used to treat children with GH deficiency (GHD) and growth failure (1, 2). Large-scale industrial production of rhGH has enabled GH treatment in thousands of patients (3). Subsequently, a high incidence of anti-GH antibody development in patients treated with first generation formulations of rhGH was reported (4). More recently, improvements in recombinant DNA technology have led to rhGH formulations with low antigenicity and patients treated with rhGH rarely develop antibodies. Case report A 12.5-year-old Italian girl was referred to our institute for progressive growth failure. She was the second child of non-consanguineous Italian parents; her brother was healthy and of normal stature. The mother was 160 cm tall and reached menarche at 13 years, and the father was 165 cm, resulting in a mid-parental target height of 156 cm. She was born at the 39th week of gestation by an uncomplicated delivery, with a birth length of 49 cm and a weight of 3250 g. Her perinatal period and neuromotor development were both normal. A progressive decrease in growth velocity was observed from the age of 6 years until the age of 12 years (4 cm/year = – 3.40 standard devi- ation score according to Tanner [(5); SDS], with a height of 128.2 cm (– 3.37 SDS), body mass index (BMI) of 16.43 (– 1.4 SDS) and a bone age of 9 years. At her first visit she was prepubertal. As some non-specific cranio-facial features and a mitral valve prolapse were found, the PTPN11 gene was analyzed, but no mutations or other polymorphisms were identified, excluding Noonan syndrome. A normal female karyotype was observed with peripheral lymphocyte culture. Furthermore, no