Pituitary-testicular function in nephropathic cystinosis.

OBJECTIVE To evaluate reproductive function in patients with cystinosis and in renal transplant recipients without cystinosis. DESIGN Cross-sectional study. SETTING Clinical Center, National Institutes of Health. PATIENTS Ten male patients, 15 to 28 years old, with nephropathic cystinosis and renal allografts formed the study group; 11 renal transplant recipients who had a primary renal disorder other than cystinosis and were matched with study patients for age and renal function served as the control group. MEASUREMENTS Tanner staging, serum gonadotropin determinations, and testosterone and testosterone-binding globulin assessments. Selected patients also had a human chorionic gonadotropin (HCG) stimulation test, a gonadotropin-releasing hormone (GnRH) stimulation test, and serial sampling for luteinizing hormone (LH). MAIN RESULTS Although testosterone levels were within normal limits in 7 of 10 patients with cystinosis, the mean testosterone level in patients with cystinosis was 11.5 +/- 2.0 nmol/L compared with 24.2 +/- 3.0 nmol/L in control patients (P < 0.005). No patient with cystinosis reached Tanner stage 5 (full pubertal development), whereas 9 of 11 control patients did. Seven of 10 patients with cystinosis had elevations in LH or follicle-stimulating hormone (FSH) levels, suggesting testicular failure. These patients also had normal LH and FSH responses after GnRH stimulation, increased LH pulse frequency, and reduced testosterone response after HCG stimulation. In comparison, only 3 of 11 control patients had minimally elevated gonadotropin levels, and all 11 had normal testosterone levels. Microscopic testicular examination in one patient showed cystine crystals, germinal dysplasia, increased fibrosis, and Leydig cell hyperplasia. CONCLUSIONS Abnormalities in the pituitary-testicular axis are common in male patients with cystinosis. These changes appear to be related to the disease cystinosis and not to treated renal failure per se.