HCG

Human Chorionic Gonadotropin

HCG (Human Chorionic Gonadotropin) is a hormonal & sexual research compound. LH mimetic — directly stimulates testicular Leydig cells to produce testosterone and maintain size/fertility.

How HCG works

LH mimetic — directly stimulates testicular Leydig cells to produce testosterone and maintain size/fertility.

Proposed benefits

Testicular function / fertility support and testosterone maintenance.

Where to get HCG

The evidence for HCG

Graded by what exists behind each claim.

✅ Clinically validated

• An approved human drug with decades of clinical use — licensed for ovulation induction, hypogonadotropic hypogonadism and cryptorchidism, with trial data behind each.
• Its use in fertility preservation during testosterone therapy is supported by published clinical series showing maintained spermatogenesis, which is why it is standard practice in that setting.

📊 Correlative data

• Extensive off-label use for testicular volume and fertility on TRT, and in post-cycle protocols. The clinical experience is consistent and long-running.
• The hCG diet is the notable failure — controlled trials showed weight loss came entirely from the 500-calorie diet, with hCG no better than placebo. Worth stating because it is the most common thing people have heard about it and it is not true.

🧪 Theoretical / extrapolated

• hCG is structurally similar to LH and binds the same receptor, so it substitutes for the pituitary signal to the testes rather than replacing the hormone downstream.
• That is why it maintains testicular function where exogenous testosterone shuts it down, and why prolonged high-dose use desensitizes Leydig cells — a receptor held on continuously stops responding, which is the argument for modest intermittent dosing.

How to read these tiers: they say how much human evidence exists, not how well something works — and ✗ flags harm, never a disappointing trial. How the evidence tiers work →

What HCG actually does

Human chorionic gonadotropin is not an analog of luteinizing hormone. It is a different hormone that binds the same receptor, and the difference between those two statements is the whole page.

What the molecule is. A polypeptide hormone produced by the human placenta and, for the approved injectable, obtained from the urine of pregnant persons Pregnyl label. It is a heterodimer: an alpha subunit essentially identical to the alpha subunit shared by LH, FSH and TSH, paired with a beta subunit that supplies the specificity. Its stated action is to stimulate the interstitial (Leydig) cells of the testis to produce androgens and the corpus luteum of the ovary to produce progesterone Pregnyl label.

Both hormones bind one receptor, LHCGR, and the receptor cannot tell them apart. That is why hCG substitutes for LH clinically Esteves 2025. What differs is residence time: hCG's beta subunit carries a carbohydrate-rich C-terminal extension that LH does not, and heavily sialylated glycans slow hepatic clearance and enlarge the molecule's hydrodynamic radius. The practical consequence is a hormone whose signal at the Leydig cell lasts a day or more where the pituitary's own pulse lasts minutes.

And that is the mechanistic trade-off nobody states. The gonadal axis is built for pulses. Endogenous LH arrives in discrete bursts and the Leydig cell recovers between them. A long-acting agonist at the same receptor delivers something the system has no evolved response to — continuous occupancy — which is the same class of problem as continuous versus intermittent PTH, and it is why Leydig-cell desensitization at high hCG exposure is a real phenomenon rather than a forum theory.

The number that makes sense of the whole compound. Intratesticular testosterone in healthy men is not slightly higher than serum testosterone. It is 1,174 nmol/L against 14.1 nmol/L — a gradient of roughly eighty-fold Coviello 2005. Spermatogenesis depends on that intratesticular concentration, not on the serum number. Exogenous testosterone raises the serum figure and shuts off the LH that maintains the intratesticular one, which is precisely why a normal or high serum testosterone tells you nothing about what is happening inside the testis.

Cell, rodent, human — and where it stops

Step one, the dose-response experiment that defines this compound, and it is unusually direct because it used testicular biopsies. Twenty-nine men received 200 mg testosterone enanthate weekly — enough to suppress gonadotropins — plus saline placebo or 125, 250 or 500 IU hCG every other day for three weeks. Intratesticular testosterone rose linearly with hCG dose (P<0.001), and the 250 IU every-other-day dose maintained intratesticular testosterone only 7% below baseline Coviello 2005.

Now put that next to the dose on the card. 250 IU every other day is roughly 875 IU per week. The commonly used range sits at 500–1000 IU per dose, several times weekly — two to five times the exposure that was shown to hold intratesticular testosterone within 7% of its starting value. The published dose-finding work points downward from common practice, not upward, and the excess buys aromatization and desensitization rather than more of the thing being protected.

Step two, the approved human indications, which are narrower than the use. The label lists three: prepubertal cryptorchidism not due to anatomical obstruction, selected cases of hypogonadotropic hypogonadism in males, and induction of ovulation in anovulatory infertile women after gonadotropin treatment Pregnyl label. The male hypogonadism regimens on the label are 500–1000 units three times weekly for three weeks then twice weekly for three weeks, or a much heavier 4000 units three times weekly for 6 to 9 months schedule Pregnyl label.

Step three, the recovery population, which is where most real use sits and where the evidence is weakest. Suppression of spermatogenesis by testosterone therapy and by anabolic-androgenic steroids, its recovery pattern after stopping, and the interventions used to speed it — selective estrogen receptor modulators, gonadotropins, assisted reproduction — are reviewed as a clinical problem rather than settled by trial Desai 2022. A separate series examined the safety of hCG monotherapy specifically in men with previous exogenous testosterone use Rainer 2022. Neither is a randomized comparison of protocols.

The obstacles. (1) The intratesticular testosterone work ran three weeks; nobody has published the same biopsy dose-response at six months. (2) The label's dosing schedules were written for hypogonadotropic hypogonadism, not for maintaining fertility alongside exogenous androgen. (3) There is no published head-to-head of hCG against gonadorelin or against a SERM for axis recovery. (4) The approved product is a urinary extract Pregnyl label; recombinant and gray-market material are not the same input and no comparison of them exists in this use.

HCG pharmacokinetics — how much of it actually gets in

The card says ~24–36 hours and the approved label carries no pharmacokinetic section at all — it is an old-format label with no half-life, no Cmax and no clearance figure Pregnyl label. So the exposure has to be reasoned from structure and from the dosing schedules that work.

What the glycosylation does. This is a glycoprotein, not a peptide, and its clearance is dominated by carbohydrate rather than by peptidase. Terminal sialic acid caps the glycans and hides the galactose residues that the hepatic asialoglycoprotein receptor uses to pull glycoproteins out of circulation; the more sialylated the preparation, the longer it circulates. Molecular size then keeps it above the glomerular filtration threshold. Neither of those is peptidase chemistry, which is why hCG behaves nothing like the small peptides elsewhere in this catalog.

The schedule is the evidence. An every-other-day injection held intratesticular testosterone within 7% of baseline for three weeks Coviello 2005, and the label's regimens are two or three times weekly Pregnyl label. A drug dosed at 48-hour intervals with a sustained effect has an effective duration on the order of a day or more — consistent with the card's figure — and the supporting evidence is the dosing interval that works, not a published curve.

Oral is zero and the reason is worth stating precisely. A glycosylated heterodimer of roughly 37 kDa is dismantled by gastric acid and pancreatic proteases, and even intact it is far too large for passive intestinal absorption. Every approved presentation is an injection Pregnyl label. Any sublingual or oral hCG product is either not hCG or not absorbed, and there is no third possibility.

One kinetic consequence with real clinical bite. Because it persists, hCG is detectable on the assay used for pregnancy testing and cross-reacts with LH immunoassays. A man injecting hCG will show an LH result that reflects the injection, not his pituitary — so an LH drawn during hCG use is uninterpretable, and the honest interval before drawing a meaningful LH is measured in weeks after the last dose, not days.

What would have to be true, and how you would know it was not

Three predictions. The first two are what a panel should show if the mechanism is working; the third is the label's own sentence, in capital letters, about the use this compound is most often bought for.

1. Total testosterone should rise and LH and FSH should fall or become uninterpretable — and if LH looks normal, the assay is lying to you. hCG stimulates Leydig cells directly Pregnyl label, so total testosterone rises while the pituitary is either suppressed by the resulting androgen or masked by assay cross-reactivity. Prediction: at 4 to 6 weeks, total testosterone up, LH and FSH low or unreadable, and estradiol up on the sensitive assay, because a stimulated Leydig cell aromatizes. If testosterone does not move at all on an adequate dose, the axis problem is not at the Leydig cell and the whole approach is aimed at the wrong organ.

2. Hematocrit is the number that decides whether to continue, and it is the one people skip. Anything that raises endogenous androgen raises red cell mass. Prediction: CBC at baseline and at 12 weeks shows a measurable hematocrit rise. This is not a hypothetical — it is the most predictable movement any androgen-raising intervention produces, and it is the one that accumulates silently.

3. The prediction that cuts hardest against the market, and it is not ours — it is the label's. The FDA-approved labeling for chorionic gonadotropin states, in capital letters, that hCG has no known effect on fat mobilization, appetite or sense of hunger, or body fat distribution, and that there is no substantial evidence that it increases weight loss beyond that of caloric restriction alone Pregnyl label. Prediction: in any comparison holding calories constant, adding hCG produces no difference in weight, in body composition or in hunger. That is a falsifiable claim, it has been tested, and it is why the sentence is on the label in capitals rather than in a footnote.

What nobody has tested yet

Four experiments that would settle live arguments and have not been run.

Whether the 250 IU finding holds past three weeks. The biopsy dose-response ran for 21 days Coviello 2005. Leydig-cell desensitization, if it happens, happens on a longer timescale than that. Nobody has repeated the study at three or six months, so the single most important dosing fact about this compound rests on a three-week window.

Whether hCG or gonadorelin better preserves the axis. One acts at the Leydig cell and bypasses the pituitary; the other acts upstream and requires the pituitary to still work. They are mechanistically different strategies with the same stated goal Esteves 2025, and there is no randomized head-to-head with a biopsy, a sperm count or an intratesticular measurement as the endpoint.

What the actual LH assay interference looks like, quantified. Everyone repeats that hCG cross-reacts with LH immunoassays. Nobody has published a table of how much interference, on which platforms, and for how many days after a dose — which is exactly the information needed to know when a post-cycle LH result means anything.

Whether urinary-derived and recombinant preparations behave the same in this use. The approved product is extracted from urine Pregnyl label; the isoform mixture of a urinary extract is not identical batch to batch, and sialylation drives clearance. A simple crossover comparing testosterone response to matched IU doses of the two would answer it and has not been published for this indication.

HCG — its own safety story, not its class's

The risks here are not injection-site risks. They are endocrine, and two of them are specific to who is taking it.

In males before puberty, the drug does exactly what it is supposed to do, which is the danger. The label instructs discontinuation if signs of precocious puberty occur during treatment for cryptorchidism, and notes that induced androgen secretion may cause fluid retention Pregnyl label. Androgen production stimulated before the epiphyses close is a permanent change to adult height, not a side effect that reverses on stopping.

In females, ovarian hyperstimulation syndrome is the named serious risk and it has a delay built into it. The label describes fluid accumulation in body cavities with severe pelvic pain, nausea, vomiting and weight gain, and instructs monitoring for at least two weeks after administration Pregnyl label. The two-week window is the part that gets lost: the syndrome can appear after the person has stopped thinking about the injection.

The androgen consequences are the same ones any androgen produces, with one difference. Because the testosterone is made by the person's own Leydig cells under a sustained stimulus, aromatization runs alongside it and estradiol rises with the testosterone rather than being separately controllable. The correct response to that is a sensitive estradiol assay and a plan, not a reflex aromatase inhibitor.

And the honest limit of the recovery use. The literature on restoring spermatogenesis after testosterone or anabolic-steroid exposure describes interventions and recovery patterns, not guaranteed outcomes Desai 2022, and the safety of hCG monotherapy in exactly that population has been examined in a case series rather than a trial Rainer 2022. Anyone using this to protect fertility should know that the endpoint that matters is a semen analysis, not a testosterone level, and that the two can disagree completely.

Sources read for this page

• Coviello AD, et al. Low-dose human chorionic gonadotropin maintains intratesticular testosterone in normal men with testosterone-induced gonadotropin suppression. Journal of Clinical Endocrinology and Metabolism 2005 · PMID 15713727
• U.S. Food and Drug Administration. PREGNYL (chorionic gonadotropin for injection, USP) — full prescribing information. DailyMed, U.S. National Library of Medicine
• Esteves SC, et al. The role of luteinizing hormone activity in spermatogenesis: from physiology to clinical practice. Reproductive Biology and Endocrinology 2025 · PMID 39800700
• Rainer Q, et al. The Safety of Human Chorionic Gonadotropin Monotherapy Among Men With Previous Exogenous Testosterone Use. Cureus 2022 · PMID 35822152
• Desai A, et al. Understanding and managing the suppression of spermatogenesis caused by testosterone replacement therapy (TRT) and anabolic-androgenic steroids (AAS). Therapeutic Advances in Urology 2022 · PMID 35783920

HCG — safety, predicted from mechanism

HCG — interference & stacking

Bloodwork to run alongside HCG

Baseline first, then again at 8–12 weeks.

The Post-Cycle / Recovery & Fertility panel covers these in one order — 9 markers, $184.50 with the discount applied.

Check results you already have → · All 103 markers A–Z

HCG — frequently asked questions

HCG inside a finished plan

One arm of 3 Protocol Blueprints, free to read in full.

What HCG is used for

HCG appears under 3 goals in the goal router.

Related Hormonal & Sexual compounds

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