Noonan syndrome males display Sertoli cell-specific primary testicular insufficiency

Context Abnormalities in the hypothalamo-pituitary-gonadal axis have long been reported in Noonan syndrome (NS) males with only few data available in prepubertal children. Objective The aim of this study was to describe the gonadal function of NS males from childhood to adulthood. Design It is a retrospective chart review. Patients and methods A total of 37 males with a genetically confirmed diagnosis of NS were included. Clinical and genetic features, as well as serum hormone levels (LH, FSH, testosterone, anti-Müllerian hormone (AMH), and inhibin B) were analysed. Results Of the 37 patients, 16 (43%) children had entered puberty at a median age of 13.5 years (range: 11.4-15.0 years); age at pubertal onset was negatively correlated with BMI SDS (r = -0.541; P = 0.022). In pubertal boys, testosterone levels were normal suggesting a normal Leydig cell function. In contrast, NS patients had significant lower levels of AMH (mean SDS: -0.6 ± 1.1; P = 0.003) and inhibin B (mean SDS: -1.1 ± 1.2; P < 0.001) compared with the general population, suggesting a Sertoli cell dysfunction. Lower AMH and inhibin B levels were found in NS-PTPN11 patients, whereas these markers did not differ from healthy children in SOS1 patients. No difference was found between cryptorchid and non-cryptorchid patients for AMH and inhibin B levels (P = 0.43 and 0.62 respectively). Four NS-PTPN11 patients had a severe primary hypogonadism with azoospermia/cryptozoospermia. Conclusions NS males display Sertoli cell-specific primary testicular insufficiency, whereas Leydig cell function seems to be unaffected.