Growth hormone (GH)-releasing hormone-induced GH response in hypothalamic amenorrhea: evidence of altered central neuromodulation

To evaluate the GH-releasing hormone (GH-RH)-induced response of GH in patients affected by hypothalamic amenorrhea. Patients affected by weight-loss-related hypothalamic amenorrhea (n=28) were studied and compared with 20 healthy controls. Among patients with weight-loss amenorrhea, both hypogonadotropic and normogonadotropic conditions were present. All subjects underwent a GH-RH test (GEREF, Serono, Rome, Italy) (1 μg/kg body weight IV). Plasma GH concentrations were determined using commercially available RIAs. Also, in selected samples insulinlike growth factor-I (IGF-I) levels were measured. Basal plasma IGF-I levels as well as body mass index (BMI) were lower in amenorrheic patients than in healthy controls. No significant correlation was found between BMI and IGF-I or E2 plasma levels or between LH and IGF-I plasma levels. The basal GH plasma levels were comparable in all groups of subjects. The GH-RH-induced GH response evaluated as maximal release and as area under the curve (AUC) was higher in amenorrheic patients than in control subjects. The amenorrheic condition associated with reduced BMI changes the GH-RH–induced GH response in hypothalamic amenorrhea, supporting a GH and a IGF-I disregulation in weight-loss–related amenorrhea.