Four weeks isn't a warm-up. It's the window where your HPG axis decides whether to fully shut down (the classic TRT trajectory) or whether the adjunct stack you're running keeps the upstream signaling alive. Testosterone enters the bloodstream and the hypothalamus reads the elevated androgen, drops GnRH pulse frequency, LH and FSH collapse, and Leydig cells stop producing intratesticular testosterone within 7-14 days. Without intervention, testicular volume drops measurably by week 4. The adjuncts — HCG, Kisspeptin-10, or Gonadorelin — exist to interrupt that cascade at different points in the axis. Weeks 1-4 is where the timing of those injections either keeps the lights on or doesn't.
What's actually happening cellularly
The exogenous testosterone you inject Monday and Thursday saturates androgen receptors and signals "abundance" to the hypothalamus. GnRH neurons reduce pulse frequency. The pituitary, no longer driven, stops releasing LH. The Leydig cells inside the testes, no longer stimulated by LH, stop converting cholesterol to pregnenolone to testosterone. Intratesticular testosterone — which is roughly 100x higher than serum testosterone in an unsuppressed system — crashes. Sperm production halts. Testicular tissue begins atrophying.
HCG bypasses the upstream blockade entirely. It mimics LH directly at the Leydig cell receptor, restarting intratesticular steroidogenesis regardless of what the hypothalamus is doing. The practitioner corpus describes 250-500 IU on TRT injection days as the standard dose — enough to maintain testicular volume and fertility potential without driving estradiol conversion into runaway territory. Expert tier.
Kisspeptin-10 works further upstream. It stimulates GnRH neurons directly — the layer above the pituitary — and the practitioner corpus describes it producing LH pulses that "mirror natural physiology" rather than the constant flatline signal HCG produces at the Leydig level. The mechanism described: kisspeptin neurons normally pulse, GnRH neurons respond, the pituitary releases LH in pulses, and the testicular machinery responds to pulses rather than continuous stimulation. This is the more physiologic intervention. Expert tier, leaning Experimental for long-term use.
The first 28 days is also when injection-site discipline either gets locked in as habit or fails. Lipodystrophy from repeated same-site injection shows up at week 3-4 as palpable hardened tissue, scar formation, and progressively worse absorption from that site. Once it forms, you can't inject there for months. Site rotation isn't a nice-to-have. It's the difference between a stack that works at week 10 and one that's running on degraded absorption by week 6.
The Weeks 1-4 stack
| Compound | Dose | Route | Frequency | Evidence Tier | Notes |
|---|---|---|---|---|---|
| Testosterone Cypionate | 50-100 mg | IM or SubQ | Mon + Thu (twice weekly, every 3rd day) | Clinical | EOD at 25-50 mg/dose is acceptable alternative for men sensitive to peak-trough swings |
| HCG | 250-500 IU | SubQ | On TRT injection days (Mon + Thu) | Expert | Lower abdomen, alternate side from testosterone injection site |
| Kisspeptin-10 | 50-100 mcg | SubQ | Daily | Experimental | Optional upstream layer. Morning preferred. Skip if running HCG and stable |
| Gonadorelin | Pulsatile (see notes) | SubQ | 2-3x daily micro-doses | Experimental | [practitioner corpus thin on exact pulsatile dosing for TRT adjunct context — track and report] |
Reconstitution note for adjuncts: Standard 5 mg vial of Kisspeptin-10 reconstituted with 2 mL bacteriostatic water yields 250 mcg per 0.1 mL (10 units on an insulin syringe). Refrigerate after reconstitution (36-46°F), use within 28-30 days, never freeze post-reconstitution.
The injection map
Lower abdomen, two inches minimum from the navel, alternating left and right. The corpus describes a clockwise rotation pattern around the navel as the standard across leading practitioner protocols.
Weekly site rotation example:
- Mon AM: Testosterone — left abdomen, 2 inches lateral and 2 inches inferior to navel
- Mon AM: HCG — right abdomen, same coordinates mirrored
- Tue-Wed: Kisspeptin-10 daily — rotate clockwise around navel (12 o'clock → 3 o'clock → 6 o'clock → 9 o'clock across the week)
- Thu AM: Testosterone — right abdomen (alternate from Mon)
- Thu AM: HCG — left abdomen
- Fri-Sun: Kisspeptin-10 daily — continue clockwise rotation
29-gauge insulin needle for SubQ adjuncts. Same syringe for drawing and injecting at this gauge. One syringe per injection — never re-use, never share a syringe between two compounds.
Daily and weekly rhythm
Morning (fasted, before food):
- TRT injection days (Mon + Thu): testosterone first, then HCG 5-10 minutes later at a separate site
- Daily: Kisspeptin-10 if running it
Evening:
- Nothing in the Weeks 1-4 core stack. Save evening slots for Phase 2 GH-axis layering in Weeks 5-10.
Sleep:
- Lights out by 10:30 PM. The HPG axis is most responsive to GnRH stimulation during the early sleep window. The practitioner corpus describes growth hormone and gonadotropin release stacking against natural sleep-time pulses — disrupting sleep in Weeks 1-4 measurably degrades the response curve.
What you should feel
Week 1:
- Mild fatigue 24-48 hours after first testosterone injection as systems recalibrate
- Possible water retention, slight facial fullness
- Testicular sensation may shift — fullness if HCG is dosed correctly, slight reduction if HCG dose is too low
Week 2:
- Energy stabilizing
- Sleep often deeper by night 8-12
- Libido baseline starting to lift, though not yet at protocol peak
- Workout recovery noticeably improved by Day 10-14
Week 3:
- Mood floor lifts. Practitioner corpus describes "dial-tone" disappearing — the low-grade hypogonadal anhedonia clearing
- Morning erections returning consistently if HCG dose is adequate
- Testicular volume holding steady (not shrinking) — this is the HCG signal
Week 4:
- Bloodwork window. Pull labs at the trough (right before Monday's injection) for the most reliable read. Tier 1 panel: total T, free T, estradiol (sensitive assay), LH, FSH, SHBG, CBC, comprehensive metabolic panel.
- Compliance audit: are you actually injecting Mon/Thu without slippage? Are sites rotating? Are you logging every dose with site, time, and subjective metrics?
What's NOT happening yet
- Strength and hypertrophy gains. Androgen receptor saturation and myonuclear addition take 8-12 weeks minimum. If you're chasing the gym effect at week 3, you're misreading the timeline.
- Estradiol fully stabilized. E2 typically swings in the first 4-6 weeks as the body adjusts to exogenous testosterone aromatization. Don't reach for an AI yet unless symptomatic and labs confirm.
- Fertility restoration. If you came in with suppressed sperm production, HCG is preserving Leydig function but spermatogenesis takes the full spermatogenic cycle (~74 days). Week 4 is too early to assess.
- Full mood and cognitive lift. The androgen receptor density in the CNS doesn't fully recalibrate until weeks 8-12. Week 4 gets you to "noticeably better." It doesn't get you to ceiling.
- The "feel" of optimization. The audience that comes off TRT Reddit expecting a switch-flip experience by week 2 is reading propaganda. The real curve is gradual, with the protocol's compounding effect becoming undeniable around week 6-8.
The Weeks 1-4 schedule is the compliance test. Skip a Thursday injection because you traveled, and trough testosterone drops measurably before Sunday. Inject in the same square inch of abdomen seven times in a row, and absorption from that site degrades for the rest of the protocol. The compounds are not the variable. The schedule is.
Research describes this. Track it. Adjust.