Trestolone
[2][3] It has been under development for potential use as a male hormonal contraceptive and in androgen replacement therapy for low testosterone levels.[4][3] Trestolone is not a substrate for 5α-reductase and hence is not potentiated or inactivated in so-called "androgenic" tissues like the skin, hair follicles, and prostate gland.[6][13] However, trestolone has only weak estrogenic activity and an amount that would appear to be insufficient for replacement purposes, as evidenced by decreased bone mineral density in men treated with it for hypogonadism.In order to render a man infertile, a hormone-based male contraceptive method must stop spermatogenesis by interrupting the release of gonadotropins from the pituitary gland.[4][3] As a result of trestolone's gonadotropin-suppressing qualities, levels of serum testosterone fall sharply in men treated with sufficient amounts of the medication.Normally, an inadequate testosterone level causes undesirable effects such as fatigue, loss of skeletal muscle mass, reduced libido, and weight gain.[8][21] Development of trestolone for potential use in male hormonal contraception and androgen replacement therapy was started by 1993, and continued thereafter.