Testosterone Enanthate (Test E, Delatestryl)

Testosterone enanthate is an intramuscular injectable testosterone preparation that's been a cornerstone of hormone replacement therapy since the 1950s. It consists of natural testosterone bound to an enanthic acid ester, which slows its release from the injection depot and extends its duration of action to approximately 1-2 weeks. The pharmacology is straightforward. After injection, esterases in blood and tissue cleave the enanthate ester, releasing free testosterone over several days. Peak serum levels occur 24-48 hours post-injection, then gradually decline. This creates a sawtooth pattern if injected weekly, which is why many modern TRT protocols use twice-weekly or every-other-day injections to flatten the curve and reduce side effects. Enanthate vs. cypionate is a common question, and the honest answer is that they're nearly interchangeable. Cypionate has a slightly longer half-life (about 5 days vs. 4.5 for enanthate) and tends to be more commonly prescribed in the US, while enanthate is more popular internationally. Some patients report subjective differences, but pharmacokinetically they're very similar. The evidence base for testosterone replacement is among the strongest in hormone therapy. The Testosterone Trials (TTrials), a coordinated set of seven randomized controlled trials funded by the NIH and published starting in 2016 (PMID: 27532802), enrolled 790 men aged 65 and older with confirmed low testosterone. The sexual function trial showed clear improvements. The vitality trial showed modest mood benefits. The bone substudy (PMID: 28241237) demonstrated a 7.5% increase in spinal volumetric bone mineral density over 12 months. The cardiovascular safety question was answered in 2023 by the TRAVERSE trial (PMID: 37326325), which enrolled 5,246 men aged 45-80 with hypogonadism and established cardiovascular disease or high cardiovascular risk. Over a mean follow-up of 33 months, testosterone replacement did not increase the rate of major adverse cardiovascular events compared to placebo. This was a landmark finding because the FDA had required a cardiovascular outcomes trial after earlier observational studies raised concerns. Bhasin et al.'s dose-response study (PMID: 11176916) remains one of the most cited papers in the field. In young men, testosterone enanthate at doses from 25 to 600 mg/week produced dose-dependent increases in lean body mass, muscle cross-sectional area, and leg press strength. Even the 125 mg/week group (roughly a standard TRT dose) gained 3.4 kg of lean mass over 20 weeks. Clinical monitoring on testosterone enanthate is well established. Standard labs include total testosterone, free testosterone (preferably by equilibrium dialysis), estradiol, hematocrit, PSA, and a comprehensive metabolic panel. Hematocrit is the most common reason for dose adjustment; polycythemia occurs in 5-15% of users and may require therapeutic phlebotomy or dose reduction. The estradiol management question divides clinicians. Some providers routinely prescribe aromatase inhibitors like anastrozole alongside testosterone. Others argue that estradiol is protective for cardiovascular and bone health and should only be suppressed if symptoms (gynecomastia, significant water retention, emotional lability) are present. The data generally supports a symptom-driven approach rather than routine AI use. HCG co-administration is standard for men who want to preserve fertility or testicular volume. Testosterone alone suppresses the HPG axis, leading to near-zero intratesticular testosterone and impaired spermatogenesis. HCG at 500-1000 IU 2-3 times weekly maintains intratesticular testosterone and, in most cases, semen parameters. Cost is one of testosterone enanthate's advantages. Generic testosterone enanthate from compounding pharmacies runs $30-80/month, making it one of the most affordable HRT options available. Brand-name Delatestryl is more expensive but rarely prescribed when generics work identically. Subcutaneous injection has gained popularity as an alternative to intramuscular. Several studies have shown comparable pharmacokinetics with smaller needles (27-30 gauge) and less injection site discomfort. Al-Futaisi et al. and others have published on SubQ testosterone showing equivalent serum levels with potentially less hematocrit elevation.