HCG (Human Chorionic Gonadotropin)

Mechanism

HCG is a hormone naturally produced during pregnancy that closely mimics luteinizing hormone (LH). In men, it stimulates the testes to produce testosterone and sperm, making it invaluable for maintaining fertility during testosterone replacement therapy or for post-cycle therapy after steroid use. In women, it triggers ovulation and is a cornerstone of fertility treatment. It also helps maintain testicular size and function in men on TRT.

Effects

REPRODUCTIVE (MALE): Primary application in peptide community. Mimics LH at the testicular Leydig cell, maintaining intratesticular testosterone (ITT) production during exogenous testosterone use — critical because TRT suppresses endogenous LH, causing testicular atrophy and infertility. RCTs show HCG 500 IU 3x/week maintains ITT at 26% of baseline vs. near-zero without it during TRT (Coviello et al., 2005). Maintains testicular volume — testicular atrophy is the most visible sign of TRT-induced suppression, often psychologically distressing. Supports spermatogenesis by maintaining ITT (sperm production requires 50-100x higher testosterone inside the testes than blood levels). Used pre-PCT to "prime" testes before Clomid/Nolvadex for faster recovery. REPRODUCTIVE (FEMALE): Triggers final oocyte maturation — mimics the LH surge that induces ovulation. Women ovulate within 36-40 hours of HCG injection (standard IVF/IUI trigger protocol). Supports corpus luteum progesterone production in early pregnancy. FDA-approved for ovulation induction. ENDOCRINE: Raises serum testosterone 50-100% within 72-96 hours of injection (dose-dependent). Increases estradiol (via aromatization of increased testosterone) — may require aromatase inhibitor management. Does NOT restore HPG axis function — it replaces LH signaling rather than restoring endogenous LH production. Sustained use can actually desensitize Leydig cells to LH (downregulation concern at very high doses). METABOLIC: Despite historical 'HCG diet' claims, the FDA has concluded there is no substantial evidence that HCG causes weight loss. The original 500-calorie 'HCG diet' (Simeons protocol, 1954) attributed weight loss to caloric restriction, not HCG itself. Any metabolic effects are secondary to testosterone normalization. MUSCULOSKELETAL: Indirect — maintains testosterone levels that support muscle protein synthesis, bone density, and strength. NEUROLOGICAL: Testosterone restoration supports cognitive function, mood, and libido. CARDIOVASCULAR: Testosterone normalization supports cardiovascular function, but supraphysiological estradiol from HCG-induced aromatization could theoretically increase clotting risk — monitor. Tier 3: Widely used in anti-aging clinics alongside TRT. Standard fertility preservation protocol during TRT. Post-cycle therapy use is ubiquitous in the performance community.

Practitioner Guide

DOSING TIPS: Three main clinical contexts: (1) TRT Adjunct — 500-1000 IU subcutaneous 2-3x/week to maintain testicular function and fertility during TRT. Most common: 500 IU every other day or 3x/week. (2) PCT Primer — 1000-2000 IU every other day for 2-3 weeks BEFORE starting SERMs (Clomid/Nolvadex), to restore testicular responsiveness. (3) Fertility — 1500-4000 IU IM 2-3x/week, often combined with HMG or FSH for spermatogenesis induction. For female ovulation trigger: single dose 5,000-10,000 IU IM. RECONSTITUTION: HCG comes as lyophilized powder with bacteriostatic water diluent. 5,000 IU vial + 5mL BAC water = 1,000 IU/mL. 10,000 IU vial + 5mL BAC water = 2,000 IU/mL. Use insulin syringe for subcutaneous injection. Reconstituted HCG must be refrigerated and used within 30 days (some say 60 days — err on the cautious side). INJECTION SITE: Subcutaneous (abdominal fat pad preferred) for TRT adjunct dosing. Intramuscular (deltoid or gluteal) for larger fertility doses. SubQ is equally effective as IM for typical doses and far more convenient. TIMING: Inject in the evening — LH naturally peaks during sleep, so evening HCG mimics physiological rhythm. On TRT: time HCG injections on days between testosterone injections for smoother hormone levels. SUPPLEMENT SYNERGIES: On TRT + HCG: may need aromatase inhibitor (anastrozole 0.25-0.5mg 2x/week) if estradiol rises above range. Zinc and vitamin D support testicular steroidogenesis. For PCT: HCG first → then Clomid 25-50mg/day + Nolvadex 20mg/day for 4-6 weeks. CYCLING: During TRT — continuous use at moderate dose (250-500 IU 2-3x/week) is standard and does not require cycling. For PCT — limited duration (2-3 weeks) before transitioning to SERMs. Prolonged high-dose HCG (>1500 IU/day) risks Leydig cell desensitization — do not exceed 3 weeks at high doses. STACKING: TRT protocol: Testosterone + HCG 500 IU 3x/week +/- AI. Fertility stack: HCG + HMG (adds FSH for Sertoli cell support). PCT: HCG 2 weeks → Clomid + Nolvadex 4-6 weeks. Anti-aging: HCG monotherapy 500-1500 IU 2-3x/week (for men who want testosterone boost without exogenous T). CONTRAINDICATION NUANCES: Prostate cancer (androgen-dependent) — absolute contraindication. Estrogen-sensitive conditions — HCG raises E2 via aromatization, monitor closely. Polycythemia — testosterone increase raises RBC production. Precocious puberty in adolescents — do not use. Certain cancers that secrete HCG (germ cell tumors) — HCG measurement is diagnostic, exogenous use confounds monitoring. STORAGE: Unreconstituted — room temperature or refrigerated, protect from light. Reconstituted — MUST refrigerate, use within 30 days. Do not freeze. PATIENT EDUCATION: HCG is not testosterone — it tells your testes to MAKE testosterone. This distinction matters: it preserves fertility while TRT alone shuts it down. Expect testicular fullness within 1-2 weeks. Blood work: check total testosterone, free testosterone, estradiol, and LH/FSH at baseline and 6-8 weeks. The most common side effect is elevated estradiol (bloating, nipple sensitivity) — easily managed with low-dose AI.

Evidence

• Intrauterine human chorionic gonadotropin administration before embryo transfer (IHABT): an individual participant data meta-analysis of randomized controlled trials.

  Zou H, Abdallah KS, Wirleitner B, Hong KH, Thanaboonyawat I, Laokirkkiat P, Hafezi M, Kokeguchi S, Makhlouf A, Libesman S, Nguyen D, Williams JG, Showell M, Gadalla M, Mol BWJ, Li W, Wang R (2026) — Human Reproduction Update — PMID: 41990228

  Across 7 trustworthy randomized trials with individual participant data (n=2244), intrauterine hCG before embryo transfer did not improve live birth or clinical pregnancy rates versus placebo or no intervention. The paper argues hCG should not be offered as an IVF add-on, making it useful counterevidence against overclaiming fertility benefit in this setting.

  strong

• Comparing the response of triple therapy and conventional treatment in male congenital hypogonadotropic hypogonadism: a randomized controlled trial.

  Konsam BD, Bhadada SK, Dutta P, Gorsi U, Baruah MM, Prasad TN, Walia R (2026) — Frontiers in Endocrinology — PMID: 41993983

  In adult males with congenital hypogonadotropic hypogonadism, triple therapy with hCG, FSH, and testosterone achieved spermatogenesis rates similar to comparator regimens but required a lower weekly hCG dose at spermatogenesis and improved quality-of-life measures. The study supports hCG as an important component of fertility-restoration regimens while underscoring that outcomes depend on combination therapy context.

  moderate

• Sublingual human chorionic gonadotropin as an adjuvant to ovulation induction.

  Ferreira PAG et al. (2024) — JBRA Assisted Reproduction — PMID: 38224574

  In a prospective double-blind randomized ovulation-induction study, sublingual HCG used with clomiphene citrate or letrozole did not significantly improve ovulation induction or pre-ovulatory follicle counts, though HCG with clomiphene showed a moderately positive correlation with endometrial thickening.

  moderate

Research Summary

TIER 1 (Gold Standard): Coviello et al., 2005 — RCT demonstrating HCG maintains intratesticular testosterone during exogenous T administration (PMID: 15713727). FDA-approved product labeling for Pregnyl, Novarel, Ovidrel. Cochrane reviews on HCG for ovulation induction in IVF protocols. Humaidan et al. — multiple RCTs on HCG trigger protocols in ART (extensive publication record). TIER 2 (Strong): Katz et al., 2011 — HCG to maintain fertility during TRT, clinical guidelines. Endocrine Society Clinical Practice Guidelines for hypogonadism mention HCG as adjunct (PMID: 29562364). Crosnoe et al., 2013 — HCG for hypogonadal men who desire fertility (PMID: 23218946). Bhasin et al., 2018 — Testosterone therapy guidelines (PMID: 29562364). TIER 3 (Moderate): Extensive use in anti-aging medicine — practitioner protocols for TRT + HCG well-established with decades of clinical experience. PCT protocols from performance medicine (clinical practice guidelines from ISSM, ASRM). International data: HCG is a global pharmaceutical with decades of post-marketing surveillance. Community protocols extensively documented. FDA advisory against HCG for weight loss (2011) — debunked the Simeons diet claim. KEY FINDINGS: (1) HCG is essential for fertility preservation during TRT. (2) It does not replace LH — it mimics LH at the receptor. (3) Weight loss claims are debunked. (4) Desensitization risk is real at high doses — use moderate doses. (5) One of the most well-studied reproductive peptides in existence. GAPS: Optimal long-term dosing for TRT adjunct not established by RCT. Long-term fertility outcomes with continuous low-dose HCG use. Leydig cell desensitization threshold in humans. ACTIVE TRIALS: Multiple ongoing trials for male infertility and TRT optimization on ClinicalTrials.gov.