Levonorgestrel implants enhanced the suppression of spermatogenesis by testosterone implants: comparison between Chinese and non-Chinese men

J Clin Endocrinol Metab. 2006 Feb;91(2):460-70. doi: 10.1210/jc.2005-1743. Epub 2005 Nov 8.


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 10(6)/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.

Publication types

  • Comparative Study
  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • China / ethnology
  • Contraception / methods*
  • Drug Implants / administration & dosage
  • Drug Implants / pharmacology
  • Drug Synergism
  • Follicle Stimulating Hormone / blood
  • Humans
  • Levonorgestrel / administration & dosage
  • Levonorgestrel / pharmacology*
  • Luteinizing Hormone / blood
  • Male
  • Middle Aged
  • Oligospermia / chemically induced
  • Sex Hormone-Binding Globulin / metabolism
  • Sperm Count
  • Spermatogenesis / drug effects*
  • Testosterone / administration & dosage
  • Testosterone / blood
  • Testosterone / pharmacology*
  • United States


  • Drug Implants
  • Sex Hormone-Binding Globulin
  • Testosterone
  • Levonorgestrel
  • Luteinizing Hormone
  • Follicle Stimulating Hormone