Neuroendocrine features of pubertal development in females with mental retardation

In order to evaluate the hypothalamic-pituitary effects of mental retardation during pubertal development, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) responses to gonadotropin-releasing hormone (GnRH) administration were evaluated at various pubertal stages in a female population with mental retardation (MR) compared to a healthy control group of adolescents. Fifty-six girls aged 8-16 years with MR and 146 normal females of the same age participated in the study. The analyzed subjects were divided into different pubertal stages, ranging from P2 to P5, in line with their degree of sexual maturation. Each patient underwent a GnRH test (100 micrograms); blood samples were collected basally and 15, 30, 60, 90 minutes after the GnRH injection. FSH and LH were assayed in each sample; the gonadotropin response to GnRH administration was evaluated as incremental area. No differences were found at any pubertal stage between the two studied groups with regard to the age, body mass index, or age at menarche. Patients with mental retardation during stages P2 and P3 showed lower FSH secretion in response to GnRH bolus compared with control subjects (P2, p < 0.05; P3, p < 0.01). In conclusion, our data show that MR is related to an impaired response of the FSH-secreting pituitary cells to their appropriate stimulus; this feature is present only in the initial pubertal stages, whereas it disappears during sexual development.