Dose effects of the gonadotropin-releasing hormone antagonist, Nal-Glu, combined with testosterone enanthate on gonadotropin levels in normal men.

OBJECTIVE

To test the hypothesis that over a 4-week treatment period, Nal-Glu GnRH antagonist ([AcD2Nal1, D4ClPhe2, D3Pal3, Arg5, DGlu6 [AA], DAla10] GnRH) at a dose of 200 micrograms/kg per day SC would suppress levels of immunologically active and biologically active LH and FSH more completely than a dose of 100 micrograms/kg per day.

DESIGN

Placebo controlled clinical study.

SETTING

A university community.

SUBJECTS

Thirty normal male volunteers.

INTERVENTIONS

We administered Nal-Glu at doses of 0, 100, and 200 micrograms/kg body weight per day in combination with T enanthate, 50 mg IM weekly, to separate groups of men (9 or 10 men per group) for 4 weeks.

RESULTS

Serum levels of immunologically active and biologically active gonadotropins were suppressed similarly in both groups of men who received Nal-Glu; this suppression was significantly greater than in the men who received placebo + T. Local side effects were more severe in the Nal-Glu 200 micrograms/kg per day group.

CONCLUSIONS

Administration of Nal-Glu in combination with T suppresses gonadotropins more completely than does T alone, but at doses > 100 micrograms/kg, gonadotropins are not suppressed additionally with larger doses of Nal-Glu. Subjects experienced greater local discomfort and side effects with the higher dosage. These findings suggest that dosages of Nal-Glu of > 100 micrograms/kg per day may have no advantage over the 100-micrograms/kg dose in a male contraceptive regimen.