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Levonorgestrel Implants Enhanced the Suppression of Spermatogenesis by Testosterone Implants: Comparison between Chinese and Non-Chinese Men

Division of Endocrinology, Departments of Medicine, Obstetrics and Gynecology, and Pediatrics, Harbor-University of California-Los Angeles Medical Center and Los Angeles Biomedical Research Institute (C.W., A.L.N., K.K.L., N.B., L.L., A.L., L.H., S.D., R.S.S.), Torrance, California 90509; and Jiangsu Family Planning Research Institute (X.H.W., J.S.T.) and First Affiliated Hospital, Nanjing Medical University (Y.G.C.), Nanjing, Jiangsu 210036, China

Address all correspondence and requests for reprints to: Christina Wang, M.D., General Clinical Research Center, Harbor-UCLA Medical Center, 1000 W. Carson Street, Torrance, California 90509. E-mail: wang{at}labiomed.org.

Context: Previous male contraceptive studies showed that progestins enhance spermatogenesis suppression by androgens in men.

Objective: We compared the efficacy of spermatogenesis suppression by the combination of levonorgestrel (LNG) with testosterone (T) implants to that by T implants alone in two different ethnic groups.

Design: This was a randomized trial performed in two centers with two treatment groups.

Settings: The study was performed at the Academic Medical Center in the United States and the Research Institute in China.

Participants: Forty non-Chinese and 40 Chinese healthy male volunteers were studied.

Interventions: Subjects were randomized to receive four LNG implants together with four T implants (inserted on d 1 and wk 15–18) vs. T implants alone for 30 wk.

Main Outcome Measures: The primary end point compared the efficiency of suppression to severe oligozoospermia (1 x 10⁶/ml) by LNG plus T implants vs. that by T implants alone. The secondary end point examined differences in spermatogenesis suppression between Chinese and non-Chinese subjects.

Results: LNG plus T implants caused more suppression of spermatogenesis to severe oligozoospermia during the treatment period than T implants alone at both sites (P < 0.02). In Chinese men, severe oligozoospermia was achieved in more than 90% of the men in both treatment groups. Suppression to severe oligozoospermia was less in the non-Chinese men (59%) after T alone (P < 0.020); this difference disappeared with combined treatment (89%). T implant extrusion occurred in six men. Acne and increased hemoglobin were the most common adverse events.

Conclusion: T implants resulted in more pronounced spermatogenesis suppression in Chinese men. Addition of LNG implants to T implants enhanced the suppression of spermatogenesis in the treatment period in both Chinese and non-Chinese men.

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