Intramuscular Testosterone Enanthate Plus Very Low Dosage Oral Levonorgestrel Suppresses Spermatogenesis Without Causing Weight Gain in Normal Young Men: A Randomized Clinical Trial

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Abstract
The development of a safe, well‐tolerated, effective, and reversible male hormonal contraceptive would be a major clinical advance for couples planning their family size and for control of population growth. High‐dosage parenteral testosterone (T) esters alone or in combination with a progestogen (eg, depot medroxyprogesterone) have been shown to confer effective and reversible male contraception in clinical trials, but these regimens are associated with weight gain and suppression of serum high‐density lipoprotein cholesterol (HDL) levels. We have previously demonstrated that intramuscular T enanthate 100 mg weekly plus oral levonorgestrel (LNG) 125, 250, or 500 μg daily suppresses spermatogenesis to levels associated with effective contraception, but there is a LNG‐dosage‐dependent effect of weight gain and HDL suppression. We hypothesized that intramuscular T enanthate 100 mg weekly plus a very low dosage of oral LNG would effectively suppress spermatogenesis in normal men without inducing weight gain or HDL suppression. We conducted a randomized trial comparing 6 months of intramuscular T enanthate (100 mg weekly) plus 31.25 μg of oral LNG daily (T+LNG 31; n = 20) or 62.5 μg of oral LNG daily (T+LNG 62; n = 21). The 2 regimens were equally effective in suppressing spermatogenesis to azoospermia, fewer than 1 million sperm/mL and fewer than 3 million sperm/mL (T+LNG 31 [60%, 85%, and 90%] vs T+LNG 62 [62%, 91%, and 95%] for azoospermia, fewer than 1 million and fewer than 3 million, respectively; P = NS). The T+LNG 31 group did not gain weight (0.25 ± 1.08 kg; P = NS compared with baseline), but the T+LNG 62 group gained 2.5 ± 0.77 kg (P < .05 compared with baseline). Serum HDL cholesterol levels declined significantly in both groups (percentage decline month 6 of treatment vs baseline: 12.0% ± 2.6% and 15.1% ± 3.0%; P < .05 for T+LNG 31 and 62 respectively). Serum low‐density lipoprotein cholesterol levels also declined in both groups (percentage decline month 6 of treatment vs baseline: 6.9 ± 3.9 and 6.0% ± 4.1%; P < .05 for T+LNG 31 and P = NS for T+LNG 62). There were no clinically significant adverse events or significant changes in hematology or chemistry profiles in either group during the study. We conclude that 1) intramuscular T plus oral LNG has a very potent synergistic effect in suppressing spermatogenesis at LNG dosages equal to or lower than dosages used in common female oral contraceptive regimens and 2) large, long‐term contraceptive efficacy trials should be conducted with a variety of androgen‐progestogen combinations including long‐acting T formulations such as depot T pellets or intramuscular T undecanoate plus depot LNG or very low dosage oral LNG.