Testosterone Enanthate

The 7-carbon heptanoate ester of endogenous testosterone. IM depot kinetics: serum peak at 24–48 h post-injection, steady-state reached after 4–5 half-lives (weeks 3–4). Once-weekly administration produces ~200 ng/dL peak-to-trough variance at 200 mg/week; trough suppression on EOD or twice-weekly splits. Aromatises via CYP19A1 at physiological rates — 0.2–0.3% substrate conversion to estradiol. Target serum E2 on protocol: 25–40 pg/mL (sensitive LC-MS/MS). Aggressive AI dosing that suppresses E2 below 20 pg/mL produces the documented side profile of arthralgia, libido loss, lipid degradation, and cognitive fog — iatrogenic hypoestrogenaemia is a bigger problem than measured hyperoestrogenaemia in most protocols. HPTA shutdown is total within 14 days and predictable; recovery timeline post-cessation is 3–6 months with SERM-based PCT, longer without. Haematocrit drift is the most consistent long-run biomarker — 3–5 percentage points per cycle, additive across cycles without donation.