Study Design
Prospective
Objectives
To determine the optimum gonadotropin releasing hormone (GnRH) dose to identify dysfunction of the hypothalamic-pituitary-gonadal axis in men with spinal cord injury (SCI).
Setting
Metropolitan Area Hospitals, New York and New Jersey, USA
Methods
SCI men [16 hypogonadal (HG=serum testosterone <12.1 nmol/L) & 14 eugonadal (EG)] and able-bodied (AB) men (27 HG & 11 EG) were studied. GnRH (10, 50, 100 μg) was randomly administered intravenously on three separate visits. Blood samples were collected post-GnRH for serum luteinizing hormone (LH) and follicular stimulating hormone (FSH).
Results
HG and EG men had a similar proportion of clinically acceptable gonadotropin responses to all three GnRH doses. The incremental gonadotropin responses to GnRH were not significantly different across the groups. However, in the SCI-HG group GnRH 100 μg resulted in the greatest integrated FSH response, and in the SCI-EG group, GnRH 50 μg resulted in the greatest integrated LH response compared with the AB groups. A consistent, but not significant, absolute increase in gonadotropin release was observed in the SCI groups at all GnRH doses.
Conclusion
Lower doses of GnRH did not improve the ability to identify clinical dysfunction of the hypothalamic-pituitary-gonadal axis. However, the absolutely higher SCI-HG FSH response to GnRH 100 μg and higher SCI-EG LH response to GnRH 50 μg, along with higher gonadotropin release at all GnRH doses, albeit not significant, suggests a hypothalamic-pituitary dysfunction in persons with SCI.