Testicular responses to hCG stimulation at varying doses in men with spinal cord injury

Abstract

Study design: Prospective.

Objectives: To test whether provocative stimulation of the testes identifies men with chronic spinal cord injury (SCI), a population in which serum testosterone concentrations are often depressed, possibly due to gonadal dysfunction. To accomplish this objective, conventional and lower than the conventional doses of human chorionic gonadotropin (hCG) were administered.

Methods: Thirty men with chronic SCI (duration of injury >1 year; 18 and 65 years old; 16 eugonadal (>12.1 nmol l^-1) and 14 hypogonadal (⩽12.1 nmol l^-1)) or able-bodied (AB) men (11 eugonadal and 27 hypogonadal) were recruited for the study. Stimulation tests were performed to quantify testicular responses to the intramuscular administration of hCG at three dose concentrations (ithat is, 400, 2000 and 4000 IU). The hCG was administered on two consecutive days, and blood was collected for serum testosterone in the early morning prior to each of the two injections; subjects returned on day 3 for a final blood sample collection.

Results: The average gonadal response in the SCI and AB groups to each dose of hCG was not significantly different in the hypogonadal or eugonadal subjects, with the mean serum testosterone concentrations in all groups demonstrating an adequate response.

Conclusions: This work confirmed the absence of primary testicular dysfunction without additional benefit demonstrated of provocative stimulation of the testes with lower than conventional doses of hCG. Our findings support prior work that suggested a secondary testicular dysfunction that occurs in a majority of those with SCI and depressed serum testosterone concentrations.

Figure 1. Serum Testosterone Responses to Stimulation by hCG at 400 IU, 2000 IU and 4000 IU

Data are presented as group mean with standard deviation bars redacted for enhanced visualization of group serum testosterone responses. Standard deviation is provided by dose (i.e., 400 IU, 2000 IU and 4000 IU) and Day (i.e., 1, 2, and 3) in each group for serum testosterone concentrations (400 IU- AB-Eugonadal: 9.0, 8.6, 6.7 nmol/l; AB- Hypogonadal: 3.3, 4.5, 6.5 nmol/l; SCI-Eugonadal: 6.2, 8.6, 9.5 nmol/l; SCI-Hypogonadal: 3.8, 6.8, 6.1 nmol/l); (2000 IU- AB-Eugonadal: 4.5, 5.2, 7.5 nmol/l; AB- Hypogonadal: 3.0, 4.5, 6.6 nmol/l; SCI-Eugonadal: 7.7, 8.2, 12.4 nmol/l; SCI-Hypogonadal: 5.2, 6.2, 10.4 nmol/l); and (4000 IU- AB-Eugonadal: 6.8, 8.6, 10.5 nmol/l; AB- Hypogonadal: 5.1, 8.6, 8.6 nmol/l; SCI-Eugonadal: 8.7, 7.2, 8.3 nmol/l; SCI-Hypogonadal: 5.2, 5.7, 7.7 nmol/l). The omnibus statistical models at each dose were statistically significant for group and time main effects, but no group by time interaction was observed. *p<0.01: SCI-Eugonadal vs. SCI-Hypogonadal; †p<0.01: SCI-Eugonadal vs. AB-Hypogonadal; ‡p<0.01: AB-Eugonadal vs. SCI-Hypogonadal; p<0.01: AB-Eugonadal vs AB-Hypogonadal.