Provocative stimulation of the hypothalamic-pituitary-testicular axis in men with spinal cord injury

Prospective study.

To determine the integrity of the hypothalamic-pituitary-testicular axis in healthy men with spinal cord injury (SCI).

Thirty healthy men with chronic SCI (37±10 years) and thirty-eight able-bodied (AB) controls (36±10 years) participated. Gonadotropin-releasing hormone (GnRH; 100 μg IV) was administered to determine gonadotropin release, and human chorionic gonadotropin (hCG; 4000 IU IM) was administered to determine testosterone (T) secretion. Responses to stimulation were categorized as 'responder' or 'non-responder' by clinical criteria. Single factor ANOVA with repeated measures was performed to identify group differences.

The proportion of responders to pituitary GnRH stimulation was similar in the SCI group (22 subjects (73%) for the follicular-stimulating hormone (FSH) and 23 subjects (76%) for the luteinizing hormone (LH) to that of the AB group. The SCI-responder group had an increased FSH response after stimulation compared with the AB-responder group (P<0.05). The SCI-responder group had a greater LH area under the curve to GnRH stimulation than the AB-responder group (P=0.06). The peak FSH response was at 60 min and the peak LH response at 30 min, regardless of group designation. All groups had similar increases in serum T concentration to hCG stimulation.

The pituitary response to stimulation in healthy men with SCI revealed an augmented FSH response; LH response only trended higher. The testicular response to provocative stimulation was similar in hypogonadal and eugondal subjects and in GnRH responders and non-responders. These findings suggest a lack of hypothalamic drive of pituitary gonadotropin release in healthy people with chronic SCI.