Mechanism

How it works

HCG binds to the luteinizing hormone/choriogonadotropin receptor (LHCGR) on Leydig cells in the testes, activating adenylyl cyclase via Gs protein coupling and elevating intracellular cAMP. This cascade stimulates steroidogenesis, promoting the conversion of cholesterol to testosterone and supporting spermatogenesis via Sertoli cell signaling. In women, HCG triggers ovulation by mimicking the LH surge, inducing follicular rupture and corpus luteum formation.

Reported in research

Benefits

Restores endogenous testosterone production suppressed by exogenous androgen use (PCT support)
Maintains testicular size and function during prolonged anabolic steroid cycles
Supports male fertility by stimulating spermatogenesis in hypogonadotropic hypogonadism
Treats female infertility by triggering ovulation in assisted reproductive technology (ART) protocols
May improve mood, libido, and well-being associated with restored endogenous testosterone levels
Used in diagnosis and treatment of cryptorchidism (undescended testes) in prepubertal males

Context, not a prescription

Dosing

Typical range: 250–500 IU every other day (on-cycle); 1000–2500 IU every other day for 2–3 weeks (PCT); 500–1000 IU 2–3x/week (fertility) (Subcutaneous, Intramuscular)
Cycle length: 2–6 weeks (PCT); ongoing as prescribed for hypogonadism
Half-life: ~24–36 hours (beta subunit half-life ~36 hours; initial half-life ~5–6 hours)

Safety

Side effects & contraindications

Possible side effects

Gynecomastia due to aromatization of HCG-stimulated testosterone to estradiol
Testicular discomfort or aching from increased steroidogenic activity
Water retention and bloating
Acne and oily skin from elevated androgen levels
Headaches and mood swings
Downregulation of LH receptors with prolonged high-dose use
Ovarian Hyperstimulation Syndrome (OHSS) in women — potentially serious
Injection site reactions (redness, swelling, irritation)

Contraindications

Hormone-sensitive cancers (prostate cancer, testicular germ cell tumors, breast cancer)
Precocious puberty or known androgen-sensitive conditions in pediatric patients
Ovarian cysts or enlargement not related to polycystic ovary syndrome (PCOS) in women
Uncontrolled thyroid or adrenal dysfunction
Hypersensitivity to HCG or any excipients
Active thromboembolic disorders (elevated estrogen from stimulation increases clot risk)

Research information, not medical advice. Always consult a licensed clinician before considering any peptide.

In depth

Full profile

What it does

Users typically notice improved libido, increased testicular volume, better mood and energy, and faster recovery of natural hormone function. Sperm counts can begin improving within 4–12 weeks in fertility contexts.

How it works

Think of your testes like a factory that produces testosterone. Your brain is normally the manager sending work orders (LH). When steroids flood the system, the factory gets no orders and shuts down. HCG is like a courier who bypasses the manager and hand-delivers work orders directly to the factory floor, keeping production running.

When injected, HCG travels through the bloodstream to the testes, where it docks onto special receptors on testosterone-producing cells (Leydig cells). This triggers those cells to ramp up testosterone production, keeps the testes from atrophying, and helps maintain sperm production. The effects are noticeable within days of starting.

What to expect

Testosterone levels begin rising within 24–72 hours of the first injection. Noticeable improvements in testicular fullness and libido typically appear within 1–2 weeks.

Days 1–3: HCG enters the bloodstream and begins binding to Leydig cell receptors. Testosterone production starts increasing. Some users notice a slight heaviness or tingling in the testes.
Weeks 1–2: Testicular volume noticeably improves. Libido and energy begin to return. Estrogen levels may also rise — watch for breast tenderness. Mood typically stabilizes.
Weeks 2–6: Full hormonal restoration effects are evident. In PCT contexts, the HPG axis begins to recover as HCG supports the transition back to natural LH production. In fertility use, sperm parameters begin improving.

Good to know

Always monitor estrogen (E2) levels with bloodwork when using HCG, and consider an aromatase inhibitor if estrogen rises excessively
Do not use HCG at high doses for prolonged periods — receptor downregulation can reduce its effectiveness
Reconstitute and store properly to maintain potency and avoid contamination
Work with a knowledgeable healthcare provider to set appropriate dosing and cycle length

Staying safe

Breast tenderness or slight enlargement (from estrogen conversion) — manageable with an aromatase inhibitor
Water retention and mild puffiness
Acne flare-ups as testosterone rises
Testicular aching or heaviness, especially early on

Avoid if you have:

People with prostate or hormone-sensitive cancers
Women with ovarian cysts (risk of dangerous ovarian overstimulation)
Anyone without medical supervision — HCG requires bloodwork monitoring

Overview

Clinically measurable increases in serum total testosterone (often 2–4x baseline in hypogonadotropic males), estradiol, and inhibin B within 72 hours. Testicular volume increases are measurable by orchidometry within 2–4 weeks of regular dosing. In idiopathic hypogonadotropic hypogonadism (IHH), HCG therapy combined with FSH can achieve sperm in ejaculate in 70–90% of men, though timeframe varies by baseline testicular volume. INSL3 (insulin-like factor 3), a Leydig cell biomarker of functional maturity, also increases with HCG therapy and may correlate with spermatogenic outcomes.

How it works

HCG acts as a molecular key that fits perfectly into the LH receptor lock on Leydig cells — in fact, it fits even better than LH itself due to its longer half-life and stronger receptor affinity, essentially holding the lock open far longer than the natural key would. This sustained receptor occupancy results in prolonged steroidogenic signaling compared to the pulsatile LH signal.

Following subcutaneous or intramuscular administration, HCG is absorbed into the systemic circulation with a bioavailability of approximately 75–85% via subq route. It has a biphasic elimination: an initial rapid distribution phase (t½ ~5–6 hours) followed by a longer elimination phase (t½ ~24–36 hours for the intact molecule; beta subunit t½ ~36 hours). It distributes primarily to the gonads, liver, and kidneys. HCG is metabolized via proteolytic degradation and renal filtration — urinary HCG metabolites are the basis for pregnancy tests. Clearance is reduced in renal impairment. The extended half-life compared to LH (~20 minutes) is attributable to extensive glycosylation (particularly sialylation) of the beta subunit, which masks proteolytic cleavage sites and reduces hepatic asialoglycoprotein receptor-mediated clearance.

Onset & timeline

Peak serum concentration occurs 4–12 hours post injection (subq slightly slower than IM). Testosterone levels begin rising within 12–24 hours, peak at 48–72 hours post-dose. Estradiol rises concurrently via aromatase activity in Leydig cells — E2 monitoring at 72+ hours post-injection is optimal for clinical assessment.

Days 1–3: Peak serum HCG concentrations achieved within 12 hours post-injection. StAR protein and CYP11A1 upregulation initiates within hours. Serum testosterone rises measurably at 24–48 hours. Estradiol begins rising concurrently. INSL3 upregulation begins.
Weeks 1–2: Sustained steroidogenic stimulation with regular dosing. Leydig cell hypertrophy and testicular volume recovery visible on ultrasound. HPG axis feedback dynamics shift — LH suppression from exogenous androgens (if applicable) begins resolving. Libido, energy, and mood correlate with rising testosterone.
Weeks 2–8: In hypogonadotropic hypogonadism: progressive spermatogenic recovery, with spermatids detectable in ejaculate by week 8–16 in responsive patients. In PCT: HPG axis normalization supported; transition to SERM after week 2–3 of HCG enables restoration of endogenous LH/FSH pulsatility. Long-term high-dose use risks LHCGR downregulation and reduced Leydig cell responsiveness.

Getting the most from it

Monitor serum testosterone, estradiol (E2), and hematocrit every 4–6 weeks during use; adjust AI co-administration based on E2 levels (target E2 20–30 pg/mL in most men)
Use pulsatile/intermittent dosing (e.g., 250 IU EOD rather than daily high-dose) to minimize LHCGR downregulation and maintain receptor sensitivity
Transition to a SERM-based PCT (clomiphene or enclomiphene) after HCG to restore endogenous hypothalamic-pituitary axis signaling via GnRH pulse normalization
In fertility protocols, combine with recombinant FSH (rFSH) when spermatogenesis is insufficient with HCG alone, particularly in men with cryptorchidism or severe hypogonadotropic hypogonadism

Common side effects

Hyperestrogenemia: HCG potently stimulates aromatase expression in Leydig cells, causing disproportionate E2 elevation relative to testosterone; co-administration of an aromatase inhibitor (anastrozole 0.25–0.5 mg EOD) is often warranted
LHCGR desensitization and downregulation with continuous high-dose exposure, reducing efficacy — pulsatile or lower-frequency dosing protocols are preferred
Gynecomastia (glandular breast tissue proliferation) secondary to elevated estradiol and potentially elevated prolactin
Iatrogenic secondary polycythemia if testosterone levels chronically supraphysiological

Mechanism of action

HCG is a heterodimeric glycoprotein consisting of a non-covalently associated alpha subunit (shared with LH, FSH, and TSH) and a unique beta subunit that confers receptor specificity. It binds with high affinity to the LHCGR (LH/CG receptor), a G-protein coupled receptor on testicular Leydig cells. LHCGR activation via Gsα coupling stimulates adenylyl cyclase, increasing intracellular cAMP, which activates PKA and downstream transcription of steroidogenic acute regulatory protein (StAR) and cytochrome P450 side-chain cleavage enzyme (CYP11A1), initiating cholesterol conversion to pregnenolone and subsequent testosterone biosynthesis. HCG also upregulates 3β-HSD and 17β-HSD enzymatic activity to drive androgen production. In Sertoli cells, paracrine testosterone signaling supports spermatogenesis, though HCG itself does not directly stimulate FSH receptors and cannot fully replace FSH for complete spermatogenesis restoration in hypogonadotropic patients.

Following subcutaneous or intramuscular administration, HCG is absorbed into the systemic circulation with a bioavailability of approximately 75–85% via subq route. It has a biphasic elimination: an initial rapid distribution phase (t½ ~5–6 hours) followed by a longer elimination phase (t½ ~24–36 hours for the intact molecule; beta subunit t½ ~36 hours). It distributes primarily to the gonads, liver, and kidneys. HCG is metabolized via proteolytic degradation and renal filtration — urinary HCG metabolites are the basis for pregnancy tests. Clearance is reduced in renal impairment. The extended half-life compared to LH (~20 minutes) is attributable to extensive glycosylation (particularly sialylation) of the beta subunit, which masks proteolytic cleavage sites and reduces hepatic asialoglycoprotein receptor-mediated clearance.

Pharmacodynamics

Peak serum concentration occurs 4–12 hours post injection (subq slightly slower than IM). Testosterone levels begin rising within 12–24 hours, peak at 48–72 hours post-dose. Estradiol rises concurrently via aromatase activity in Leydig cells — E2 monitoring at 72+ hours post-injection is optimal for clinical assessment.

Clinically measurable increases in serum total testosterone (often 2–4x baseline in hypogonadotropic males), estradiol, and inhibin B within 72 hours. Testicular volume increases are measurable by orchidometry within 2–4 weeks of regular dosing. In idiopathic hypogonadotropic hypogonadism (IHH), HCG therapy combined with FSH can achieve sperm in ejaculate in 70–90% of men, though timeframe varies by baseline testicular volume. INSL3 (insulin-like factor 3), a Leydig cell biomarker of functional maturity, also increases with HCG therapy and may correlate with spermatogenic outcomes.

Timeline

Days 1–3: Peak serum HCG concentrations achieved within 12 hours post-injection. StAR protein and CYP11A1 upregulation initiates within hours. Serum testosterone rises measurably at 24–48 hours. Estradiol begins rising concurrently. INSL3 upregulation begins.
Weeks 1–2: Sustained steroidogenic stimulation with regular dosing. Leydig cell hypertrophy and testicular volume recovery visible on ultrasound. HPG axis feedback dynamics shift — LH suppression from exogenous androgens (if applicable) begins resolving. Libido, energy, and mood correlate with rising testosterone.
Weeks 2–8: In hypogonadotropic hypogonadism: progressive spermatogenic recovery, with spermatids detectable in ejaculate by week 8–16 in responsive patients. In PCT: HPG axis normalization supported; transition to SERM after week 2–3 of HCG enables restoration of endogenous LH/FSH pulsatility. Long-term high-dose use risks LHCGR downregulation and reduced Leydig cell responsiveness.

Comparisons

HCG — effectiveness Very High, safety Moderate, cost $$, Medium to use
Gonadorelin (GnRH) — effectiveness High, safety Good, cost $$$, Low to use
Enclomiphene — effectiveness High, safety Good, cost $$, Low to use

Adverse effects

Common:

Hyperestrogenemia: HCG potently stimulates aromatase expression in Leydig cells, causing disproportionate E2 elevation relative to testosterone; co-administration of an aromatase inhibitor (anastrozole 0.25–0.5 mg EOD) is often warranted
LHCGR desensitization and downregulation with continuous high-dose exposure, reducing efficacy — pulsatile or lower-frequency dosing protocols are preferred
Gynecomastia (glandular breast tissue proliferation) secondary to elevated estradiol and potentially elevated prolactin
Iatrogenic secondary polycythemia if testosterone levels chronically supraphysiological

Rare:

Ovarian Hyperstimulation Syndrome (OHSS) in women: potentially life-threatening in hypersensitive patients; incidence in IVF protocols ~1–2% severe cases
Testicular torsion (exceedingly rare, case reports only, possibly related to rapid testicular volume change)
Anaphylaxis/hypersensitivity reactions to HCG protein or excipients (~<0.1% incidence)
Thromboembolism secondary to supraphysiological estrogen in susceptible individuals

Contraindications & risk mitigation

Contraindicated in:

Men with androgen-sensitive malignancies (prostate adenocarcinoma, Leydig cell tumors) — HCG stimulates tumor growth via androgenic and direct LH receptor signaling
Women with OHSS risk factors, ovarian insufficiency, or pituitary/hypothalamic dysfunction requiring precise gonadotropin control
Patients with documented hypersensitivity to gonadotropins or human-derived glycoproteins
Men on exogenous testosterone therapy seeking spermatogenesis — HCG must replace or accompany TRT, not be added to a protocol where LH suppression is complete without testicular stimulation planning

Monitor serum testosterone, estradiol (E2), and hematocrit every 4–6 weeks during use; adjust AI co-administration based on E2 levels (target E2 20–30 pg/mL in most men)
Use pulsatile/intermittent dosing (e.g., 250 IU EOD rather than daily high-dose) to minimize LHCGR downregulation and maintain receptor sensitivity
Transition to a SERM-based PCT (clomiphene or enclomiphene) after HCG to restore endogenous hypothalamic-pituitary axis signaling via GnRH pulse normalization
In fertility protocols, combine with recombinant FSH (rFSH) when spermatogenesis is insufficient with HCG alone, particularly in men with cryptorchidism or severe hypogonadotropic hypogonadism

Qué hace

Users typically notice improved libido, increased testicular volume, better mood and energy, and faster recovery of natural hormone function. Sperm counts can begin improving within 4–12 weeks in fertility contexts.

Cómo funciona

Think of your testes like a factory that produces testosterone. Your brain is normally the manager sending work orders (LH). When steroids flood the system, the factory gets no orders and shuts down. HCG is like a courier who bypasses the manager and hand-delivers work orders directly to the factory floor, keeping production running.

When injected, HCG travels through the bloodstream to the testes, where it docks onto special receptors on testosterone-producing cells (Leydig cells). This triggers those cells to ramp up testosterone production, keeps the testes from atrophying, and helps maintain sperm production. The effects are noticeable within days of starting.

Qué esperar

Testosterone levels begin rising within 24–72 hours of the first injection. Noticeable improvements in testicular fullness and libido typically appear within 1–2 weeks.

Days 1–3: HCG enters the bloodstream and begins binding to Leydig cell receptors. Testosterone production starts increasing. Some users notice a slight heaviness or tingling in the testes.
Weeks 1–2: Testicular volume noticeably improves. Libido and energy begin to return. Estrogen levels may also rise — watch for breast tenderness. Mood typically stabilizes.
Weeks 2–6: Full hormonal restoration effects are evident. In PCT contexts, the HPG axis begins to recover as HCG supports the transition back to natural LH production. In fertility use, sperm parameters begin improving.

Bueno saber

Always monitor estrogen (E2) levels with bloodwork when using HCG, and consider an aromatase inhibitor if estrogen rises excessively
Do not use HCG at high doses for prolonged periods — receptor downregulation can reduce its effectiveness
Reconstitute and store properly to maintain potency and avoid contamination
Work with a knowledgeable healthcare provider to set appropriate dosing and cycle length

Manteniéndose seguro

Breast tenderness or slight enlargement (from estrogen conversion) — manageable with an aromatase inhibitor
Water retention and mild puffiness
Acne flare-ups as testosterone rises
Testicular aching or heaviness, especially early on

Evitar si tienes:

People with prostate or hormone-sensitive cancers
Women with ovarian cysts (risk of dangerous ovarian overstimulation)
Anyone without medical supervision — HCG requires bloodwork monitoring

Descripción general

Clinically measurable increases in serum total testosterone (often 2–4x baseline in hypogonadotropic males), estradiol, and inhibin B within 72 hours. Testicular volume increases are measurable by orchidometry within 2–4 weeks of regular dosing. In idiopathic hypogonadotropic hypogonadism (IHH), HCG therapy combined with FSH can achieve sperm in ejaculate in 70–90% of men, though timeframe varies by baseline testicular volume. INSL3 (insulin-like factor 3), a Leydig cell biomarker of functional maturity, also increases with HCG therapy and may correlate with spermatogenic outcomes.

Cómo funciona

HCG acts as a molecular key that fits perfectly into the LH receptor lock on Leydig cells — in fact, it fits even better than LH itself due to its longer half-life and stronger receptor affinity, essentially holding the lock open far longer than the natural key would. This sustained receptor occupancy results in prolonged steroidogenic signaling compared to the pulsatile LH signal.

Following subcutaneous or intramuscular administration, HCG is absorbed into the systemic circulation with a bioavailability of approximately 75–85% via subq route. It has a biphasic elimination: an initial rapid distribution phase (t½ ~5–6 hours) followed by a longer elimination phase (t½ ~24–36 hours for the intact molecule; beta subunit t½ ~36 hours). It distributes primarily to the gonads, liver, and kidneys. HCG is metabolized via proteolytic degradation and renal filtration — urinary HCG metabolites are the basis for pregnancy tests. Clearance is reduced in renal impairment. The extended half-life compared to LH (~20 minutes) is attributable to extensive glycosylation (particularly sialylation) of the beta subunit, which masks proteolytic cleavage sites and reduces hepatic asialoglycoprotein receptor-mediated clearance.

Inicio y cronología

Peak serum concentration occurs 4–12 hours post injection (subq slightly slower than IM). Testosterone levels begin rising within 12–24 hours, peak at 48–72 hours post-dose. Estradiol rises concurrently via aromatase activity in Leydig cells — E2 monitoring at 72+ hours post-injection is optimal for clinical assessment.

Days 1–3: Peak serum HCG concentrations achieved within 12 hours post-injection. StAR protein and CYP11A1 upregulation initiates within hours. Serum testosterone rises measurably at 24–48 hours. Estradiol begins rising concurrently. INSL3 upregulation begins.
Weeks 1–2: Sustained steroidogenic stimulation with regular dosing. Leydig cell hypertrophy and testicular volume recovery visible on ultrasound. HPG axis feedback dynamics shift — LH suppression from exogenous androgens (if applicable) begins resolving. Libido, energy, and mood correlate with rising testosterone.
Weeks 2–8: In hypogonadotropic hypogonadism: progressive spermatogenic recovery, with spermatids detectable in ejaculate by week 8–16 in responsive patients. In PCT: HPG axis normalization supported; transition to SERM after week 2–3 of HCG enables restoration of endogenous LH/FSH pulsatility. Long-term high-dose use risks LHCGR downregulation and reduced Leydig cell responsiveness.

Cómo aprovecharlo al máximo

Monitor serum testosterone, estradiol (E2), and hematocrit every 4–6 weeks during use; adjust AI co-administration based on E2 levels (target E2 20–30 pg/mL in most men)
Use pulsatile/intermittent dosing (e.g., 250 IU EOD rather than daily high-dose) to minimize LHCGR downregulation and maintain receptor sensitivity
Transition to a SERM-based PCT (clomiphene or enclomiphene) after HCG to restore endogenous hypothalamic-pituitary axis signaling via GnRH pulse normalization
In fertility protocols, combine with recombinant FSH (rFSH) when spermatogenesis is insufficient with HCG alone, particularly in men with cryptorchidism or severe hypogonadotropic hypogonadism

Efectos secundarios comunes

Hyperestrogenemia: HCG potently stimulates aromatase expression in Leydig cells, causing disproportionate E2 elevation relative to testosterone; co-administration of an aromatase inhibitor (anastrozole 0.25–0.5 mg EOD) is often warranted
LHCGR desensitization and downregulation with continuous high-dose exposure, reducing efficacy — pulsatile or lower-frequency dosing protocols are preferred
Gynecomastia (glandular breast tissue proliferation) secondary to elevated estradiol and potentially elevated prolactin
Iatrogenic secondary polycythemia if testosterone levels chronically supraphysiological

Mecanismo de acción

HCG is a heterodimeric glycoprotein consisting of a non-covalently associated alpha subunit (shared with LH, FSH, and TSH) and a unique beta subunit that confers receptor specificity. It binds with high affinity to the LHCGR (LH/CG receptor), a G-protein coupled receptor on testicular Leydig cells. LHCGR activation via Gsα coupling stimulates adenylyl cyclase, increasing intracellular cAMP, which activates PKA and downstream transcription of steroidogenic acute regulatory protein (StAR) and cytochrome P450 side-chain cleavage enzyme (CYP11A1), initiating cholesterol conversion to pregnenolone and subsequent testosterone biosynthesis. HCG also upregulates 3β-HSD and 17β-HSD enzymatic activity to drive androgen production. In Sertoli cells, paracrine testosterone signaling supports spermatogenesis, though HCG itself does not directly stimulate FSH receptors and cannot fully replace FSH for complete spermatogenesis restoration in hypogonadotropic patients.

Following subcutaneous or intramuscular administration, HCG is absorbed into the systemic circulation with a bioavailability of approximately 75–85% via subq route. It has a biphasic elimination: an initial rapid distribution phase (t½ ~5–6 hours) followed by a longer elimination phase (t½ ~24–36 hours for the intact molecule; beta subunit t½ ~36 hours). It distributes primarily to the gonads, liver, and kidneys. HCG is metabolized via proteolytic degradation and renal filtration — urinary HCG metabolites are the basis for pregnancy tests. Clearance is reduced in renal impairment. The extended half-life compared to LH (~20 minutes) is attributable to extensive glycosylation (particularly sialylation) of the beta subunit, which masks proteolytic cleavage sites and reduces hepatic asialoglycoprotein receptor-mediated clearance.

Farmacodinamia

Peak serum concentration occurs 4–12 hours post injection (subq slightly slower than IM). Testosterone levels begin rising within 12–24 hours, peak at 48–72 hours post-dose. Estradiol rises concurrently via aromatase activity in Leydig cells — E2 monitoring at 72+ hours post-injection is optimal for clinical assessment.

Clinically measurable increases in serum total testosterone (often 2–4x baseline in hypogonadotropic males), estradiol, and inhibin B within 72 hours. Testicular volume increases are measurable by orchidometry within 2–4 weeks of regular dosing. In idiopathic hypogonadotropic hypogonadism (IHH), HCG therapy combined with FSH can achieve sperm in ejaculate in 70–90% of men, though timeframe varies by baseline testicular volume. INSL3 (insulin-like factor 3), a Leydig cell biomarker of functional maturity, also increases with HCG therapy and may correlate with spermatogenic outcomes.

Cronología

Days 1–3: Peak serum HCG concentrations achieved within 12 hours post-injection. StAR protein and CYP11A1 upregulation initiates within hours. Serum testosterone rises measurably at 24–48 hours. Estradiol begins rising concurrently. INSL3 upregulation begins.
Weeks 1–2: Sustained steroidogenic stimulation with regular dosing. Leydig cell hypertrophy and testicular volume recovery visible on ultrasound. HPG axis feedback dynamics shift — LH suppression from exogenous androgens (if applicable) begins resolving. Libido, energy, and mood correlate with rising testosterone.
Weeks 2–8: In hypogonadotropic hypogonadism: progressive spermatogenic recovery, with spermatids detectable in ejaculate by week 8–16 in responsive patients. In PCT: HPG axis normalization supported; transition to SERM after week 2–3 of HCG enables restoration of endogenous LH/FSH pulsatility. Long-term high-dose use risks LHCGR downregulation and reduced Leydig cell responsiveness.

Comparaciones

HCG — efectividad Very High, seguridad Moderate, costo $$, Medium de usar
Gonadorelin (GnRH) — efectividad High, seguridad Good, costo $$$, Low de usar
Enclomiphene — efectividad High, seguridad Good, costo $$, Low de usar

Efectos adversos

Comunes:

Hyperestrogenemia: HCG potently stimulates aromatase expression in Leydig cells, causing disproportionate E2 elevation relative to testosterone; co-administration of an aromatase inhibitor (anastrozole 0.25–0.5 mg EOD) is often warranted
LHCGR desensitization and downregulation with continuous high-dose exposure, reducing efficacy — pulsatile or lower-frequency dosing protocols are preferred
Gynecomastia (glandular breast tissue proliferation) secondary to elevated estradiol and potentially elevated prolactin
Iatrogenic secondary polycythemia if testosterone levels chronically supraphysiological

Raros:

Ovarian Hyperstimulation Syndrome (OHSS) in women: potentially life-threatening in hypersensitive patients; incidence in IVF protocols ~1–2% severe cases
Testicular torsion (exceedingly rare, case reports only, possibly related to rapid testicular volume change)
Anaphylaxis/hypersensitivity reactions to HCG protein or excipients (~<0.1% incidence)
Thromboembolism secondary to supraphysiological estrogen in susceptible individuals

Contraindicaciones y mitigación de riesgos

Contraindicado en:

Men with androgen-sensitive malignancies (prostate adenocarcinoma, Leydig cell tumors) — HCG stimulates tumor growth via androgenic and direct LH receptor signaling
Women with OHSS risk factors, ovarian insufficiency, or pituitary/hypothalamic dysfunction requiring precise gonadotropin control
Patients with documented hypersensitivity to gonadotropins or human-derived glycoproteins
Men on exogenous testosterone therapy seeking spermatogenesis — HCG must replace or accompany TRT, not be added to a protocol where LH suppression is complete without testicular stimulation planning

Monitor serum testosterone, estradiol (E2), and hematocrit every 4–6 weeks during use; adjust AI co-administration based on E2 levels (target E2 20–30 pg/mL in most men)
Use pulsatile/intermittent dosing (e.g., 250 IU EOD rather than daily high-dose) to minimize LHCGR downregulation and maintain receptor sensitivity
Transition to a SERM-based PCT (clomiphene or enclomiphene) after HCG to restore endogenous hypothalamic-pituitary axis signaling via GnRH pulse normalization
In fertility protocols, combine with recombinant FSH (rFSH) when spermatogenesis is insufficient with HCG alone, particularly in men with cryptorchidism or severe hypogonadotropic hypogonadism

Reference data

Specifications

Molecular formula: Heterodimeric glycoprotein (alpha subunit ~92 aa, beta subunit ~145 aa); approximate formula C1105H1770N312O336S26
Molecular weight: ~36,700–38,000 Da (varies with glycosylation)
Half-life: ~24–36 hours (beta subunit half-life ~36 hours; initial half-life ~5–6 hours)
Route: Subcutaneous, Intramuscular
Cycle length: 2–6 weeks (PCT); ongoing as prescribed for hypogonadism
Storage: Lyophilized (powder) form: store at 2–8°C (refrigerated), protected from light; stable at room temperature for short periods prior to reconstitution. After reconstitution with bacteriostatic water: refrigerate at 2–8°C and use within 30–60 days. Do not freeze reconstituted solution.
Legal status: FDA-approved prescription medication in the United States for specific indications (hypogonadism, cryptorchidism, female infertility); compounded HCG was restricted by the FDA in 2020 but brand products (Pregnyl, Novarel, Ovidrel) remain legal by prescription. Classified as a performance-enhancing drug and banned by WADA in sports.

FAQ

Common questions

Why is HCG more effective than exogenous LH for testicular stimulation?

HCG has a much longer half-life than LH (~36 hours vs. ~20 minutes) due to extensive sialylation of its beta subunit, which reduces hepatic and renal clearance. This provides sustained LHCGR occupancy, producing a more robust and prolonged steroidogenic response per injection. LH's pulsatile nature is essential for hypothalamic feedback but disadvantageous for direct Leydig cell stimulation in hypogonadotropic states.

Can HCG alone restore full spermatogenesis in hypogonadotropic hypogonadism?

HCG alone is sufficient in approximately 50–60% of hypogonadotropic men to achieve sperm in ejaculate, as Sertoli cells respond to paracrine testosterone. However, full quantitative spermatogenesis typically requires co-administration of FSH (recombinant FSH or menotropins) to directly stimulate Sertoli cell FSH receptors, particularly in men with very small testes (<4 mL) or cryptorchidism history. (Liu PY et al., J Clin Endocrinol Metab, 2009)

What is the clinical relevance of LHCGR desensitization with HCG?

Prolonged exposure to supraphysiological HCG concentrations (e.g., continuous high-dose administration) causes receptor internalization and cAMP pathway desensitization via beta-arrestin recruitment and receptor phosphorylation. This reduces steroidogenic output despite maintained HCG levels. Pulsatile or lower-frequency dosing (EOD rather than daily) preserves receptor sensitivity. This is why bodybuilding protocols using 250–500 IU EOD are pharmacologically more rational than continuous daily dosing.

How does compounded HCG differ from pharmaceutical HCG, and what are the 2020 FDA restrictions?

In 2020, the FDA removed HCG from the category of drugs eligible for pharmacy compounding under FDCA Section 503A/503B, citing that FDA-approved alternatives exist. This effectively ended widespread compounding pharmacy supply of HCG. Brand-name products (Pregnyl, Novarel, Ovidrel) remain available by prescription. This significantly increased patient cost and access barriers, driving some use of alternative agents like gonadorelin or kisspeptin-10 for HPG axis support.

What is the evidence level?

This compound is classified as Clinical evidence. Randomized controlled trial data in humans exists and supports use in specific contexts.

Research

Research & sources

Clinical evidence

Current evidence for Human Chorionic Gonadotropin (HCG) is rated as Clinical evidence. Human clinical evidence supports the reported effects.

1. Recombinant human chorionic gonadotropin treatment of men with idiopathic normosmic hypogonadotropic hypogonadism (2009) — Liu PY et al. J Clin Endocrinol Metab. 2009;94(12):4837-4845.
2. Human chorionic gonadotropin structure and function (2010) — Cole LA. Clin Chim Acta. 2010;411(1-2):48-65.
3. Recovery of spermatogenesis following testosterone replacement therapy or anabolic-androgenic steroid use (2015) — Rahnema CD et al. Asian J Androl. 2015;17(6):825-829. DOI:10.4103/1008-682X.153313
4. The use of human chorionic gonadotropin for the induction of ovulation (2012) — Papanikolaou EG et al. Hum Reprod Update. 2012;18(5):507-515.
5. LHCGR desensitization by high-dose hCG (2003) — Dufau ML. Endocr Rev. 1998;19(5):508-532. (foundational receptor biology reference)

Explore

Often discussed alongside

Gonadorelin · sexual