As there are limitations to current methods of male contraception, research has been undertaken to develop hormonal contraceptives for men, analogous to the methods for women based on estrogen and progestogens. When testosterone is administered to a man, it functions as a contraceptive by suppressing the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland. Since these hormones are the main stimulatory signals for spermatogenesis, low levels of LH and FSH markedly impair sperm production. After 3-4 months of testosterone treatment, 60-70% of men no longer have sperm in their ejaculate, and most other men exhibit markedly diminished sperm counts. Male hormonal contraception is well tolerated, free of serious adverse side effects, and 95% effective in the prevention of pregnancy. Importantly, male hormonal contraception is reversible, with sperm counts usually recovering within 4 months of the discontinuation of hormone treatment. Because exogenous testosterone administration alone does not completely suppress sperm production in all men, researchers have combined testosterone with second agents, such as progestogens or gonadotropin-releasing-hormone antagonists, to further suppress secretion of LH and FSH and improve suppression of spermatogenesis. Recent trials have used combinations of long-acting injectable or implantable forms of testosterone with progestogens, which can be administered orally, by injection or by a long-acting implant. Such combinations suppress spermatogenesis to zero without severe side effects in 80-90% of men, with near-complete suppression in the remainder of individuals. One of these testosterone and progestogen combination regimens might soon bring the promise of male hormonal contraception to fruition.

译文

由于目前男性避孕方法存在局限性,因此已经进行了研究以开发针对男性的激素避孕药,类似于基于雌激素和孕激素的女性避孕方法。当向男性施用睾丸激素时,它通过抑制垂体的促黄体激素 (LH) 和促卵泡激素 (FSH) 的分泌而起到避孕作用。由于这些激素是精子发生的主要刺激信号,因此低水平的LH和FSH明显损害了精子的产生。经过3-4个月的睾酮治疗后,60-70% 的男性射精中不再有精子,大多数其他男性的精子数量明显减少。男性激素避孕耐受性良好,无严重不良副作用,95% 有效预防妊娠。重要的是,男性激素避孕是可逆的,精子数量通常在停止激素治疗后4个月内恢复。由于单独使用外源性睾丸激素并不能完全抑制所有男性的精子产生,因此研究人员已将睾丸激素与第二种药物 (例如孕激素或促性腺激素释放激素拮抗剂) 结合使用,以进一步抑制LH和FSH的分泌并改善精子发生的抑制。最近的试验使用了长效可注射或可植入形式的睾丸激素与孕激素的组合,可以口服,注射或长效植入物给药。在80-90% 的男性中,这种组合将精子发生抑制为零,而没有严重的副作用,在其余个体中几乎完全抑制。这些睾丸激素和孕激素联合疗法之一可能很快就会实现男性激素避孕的希望。

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