Long Term HCG Use in Men - Does it Stop Working Due to Desensitization?

Online forums have spread a lot of misinformation about long term use of human chorionic gonadotropin (HCG) losing its effectiveness after weeks of use in men with or without testosterone replacement therapy. But, are those rumors based on actual studies? We will review three studies below. HCG is prescribed as sole therapy in some men to boost their own testosterone production and also in men on testosterone therapy who want to preserve fertility (healthy sperm counts) and testicular size (preventing testicular shrinkage or atrophy).

Evidence Fact Sheet: HCG and the Leydig Cell Desensitization Myth​

1. Introduction: The "Desensitization" Claim vs. Clinical Reality​

In the realm of androgen replacement, a persistent myth suggests that Human Chorionic Gonadotropin (HCG) is a double-edged sword. Online "authorities" frequently warn that long-term HCG use will eventually "fry" the Leydig cells, leading to a permanent state of desensitization where the testes no longer respond to luteinizing hormone (LH) signals. This fear-based narrative often leads patients to unnecessarily cycle the medication or avoid it altogether.
In clinical reality, HCG is a vital therapeutic tool used for:

• Intratesticular Testosterone Preservation: Maintaining natural production during TRT.
• Fertility Maintenance: Supporting spermatogenesis by mimicking LH.
• Prevention of Testicular Atrophy: Maintaining organ volume and cellular activity.

Far from destroying the Leydig cells, HCG keeps the testicular machinery "awake" during exogenous testosterone use. The disconnect between clinical success and online anxiety is a classic case of biological data being stripped of its context.
Transition: To trace the lineage of this error, we must isolate the specific data point from 1977 that has been stripped of its biological context.
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2. Deconstructing the Origin: The 1977 Haour et al. Rat Study​

The primary source of the desensitization myth is a 1977 study titled "hCG-Dependent regulation of gonadotropin receptor sites." While the study provided valuable insights into receptor dynamics, its findings have been grossly misinterpreted by the lay public.

Key Data Points from the Haour Study:

• The Subject: The researchers used prepubertal male rats, whose endocrine systems are in a state of rapid development and are not biologically identical to adult human males.
• The Immediate Effect: Following a single injection of 500 IU of HCG, binding sites in the Leydig cell membranes decreased to less than 10% of control values within 10 hours.
• The "120-Hour Recovery": Crucially, this was not permanent. Binding sites returned to normal levels by approximately 120 hours post-injection.
• The "Paradoxical Increase": Despite the low receptor count, a secondary spike in testosterone (20–30 ng/ml) occurred between 48 and 120 hours, proving the cells remained functionally responsive even with reduced receptor density.

The Extrapolation Error: The Absurdity of the Math As educators, we must highlight the massive dosage disparity. A 500 IU dose for a 300g (0.3kg) rat equals approximately 1,666 IU per kilogram. For a standard 80kg human male, a comparable dose would be over 133,000 IU in a single injection. Comparing the biological reaction of a prepubertal rat receiving 133,000 IU to a human patient receiving a standard therapeutic dose of 250–500 IU is scientifically illiterate.
Transition: While the rat data shows a temporary 120-hour recovery cycle under extreme conditions, long-term human clinical observations reveal a consistent pattern of functional durability.

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3. Evidence from Human Clinical Trials: Long-Term Outcomes​

When we move from rodents to humans, the "desensitization" theory collapses under the weight of long-term longitudinal data.

Title/Year	Patient Profile	Duration & Dosage	Key Findings regarding Desensitization
A Study of Human Testicular Function... (1966)	Two adult men with severe hypogonadotrophic hypogonadism (persisting infantilism).	One patient for 23 months; one for 6 months. High-dose HCG, later HMG/HCG combo.	HMG alone had little effect. Complete gonadal maturation required the addition of HCG. Long-term treatment produced no lasting negative effects or loss of Leydig cell function.
The Effect of Short and Long Term HCG Administration... (1974)	Klinefelter’s syndrome patients and secondary hypogonadism patients.	Chronic administration: 1500 IU, 3 times weekly.	Leydig cells in Klinefelter patients retained a functional reserve. Levels remained significantly higher than pre-treatment baselines throughout the study.

Synthesizing the Smals et al. (1974) Findings The Smals study provides a definitive rebuttal to the idea of HCG "failing." While the researchers observed that testosterone levels in Klinefelter patients tended to decrease slightly from their initial treatment peak as therapy continued, the levels remained higher than pre-treatment values. This indicates that the Leydig cells were not becoming "exhausted" but were reaching a new, elevated steady state. Even in Klinefelter patients—who have compromised testicular function—the "functional reserve" was maintained over the long term.

Transition: These clinical findings provide the foundation for why modern medical experts view the desensitization theory as a fundamental misunderstanding of biological feedback loops.
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4. Synthesis: Why the Myth Persists vs. What the Evidence Says​

The "desensitization" theory is considered flawed by experts for three primary reasons:

1. Dose and Species Disparity: There is no clinical basis for applying a 1,666 IU/kg rat dose to human TRT protocols. Human doses are orders of magnitude lower and do not trigger the extreme down-regulation seen in animal models.
2. The 120-Hour Receptor Recovery: Critics of HCG mistake "temporary downregulation" for "permanent desensitization." Think of this as a biological thermostat: the system temporarily turns down the "heat" (receptors) when there is an abundance of signal, but the machine is not broken. Receptors cycle back to normal within days.
3. Human Clinical Longevity: Studies spanning 23+ months demonstrate that Leydig cells continue to mature and function without "burning out," even at dosages higher than those typically used in modern TRT.

Technical Nuance: Enzymatic vs. Receptor Changes It is important to distinguish between the Leydig cell membrane (where receptors live) and the enzymatic pathways within the cell. Researchers like Saez and Forest (1979) identified that HCG can induce "steroidogenic desensitization" via estradiol-induced enzyme inhibition. However, this effect is dose-dependent. At standard human TRT doses, the increase in estradiol is generally insufficient to cause significant enzymatic inhibition, ensuring the HCG continues to "work" effectively for years.
Transition: For the aspiring learner, these findings clarify the distinction between short-term receptor occupancy and long-term testicular health.
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5. Final Takeaways for the Aspiring Learner​

When evaluating HCG myths, keep these three insights at the forefront of your clinical reasoning:

1. Down-regulation is Not Damage: A temporary decrease in HCG receptors is a homeostatic adjustment, not cellular destruction. The Leydig cell is a resilient organ, not a fuse that "blows" when stimulated.
2. Contextualize the Research: If a claim of "desensitization" relies on rat studies, calculate the IU/kg dose. You will likely find the dose is 500x higher than what is used in human medicine.
3. The Baseline Safety Net: Evidence shows that most men who discontinue HCG and testosterone return to their pre-treatment baseline without lasting negative effects. In many cases, HCG use during TRT makes the recovery of natural function easier by keeping the Leydig cells in a functional, "ready" state compared to the profound atrophy seen with testosterone-only protocols.

BACKGROUND INFORMATION:


The Use of HCG in Men


This Study Of Two People Did not Show Issues After 23 Months of High Doses:


A STUDY OF HUMAN TESTICULAR FUNCTION BY THE USE OF HUMAN MENOPAUSAL GONADOTROPHIN AND OF HUMAN CHORIONIC GONADOTROPHIN IN MALE HYPOGONADOTROPHIC EUNUCHOIDISM AND INFANTILISM in: European Journal of Endocrinology Volume 53 Issue 2 (1966)

Abstract

Two adult men with severe hypogonadotrophic hypogonadism (persisting infantilism) were observed during long-term treatment with chorionic gonadotrophin (HCG) (23 and 6 months respectively) followed by treatment with human menopausal gonadotrophin (HMG) (for 7 and 12 months) and finally by combined treatment with

HMG plus HCG (for 12 and 9 months). A study of hormone excretion, testicular biopsies and the clinical course showed that HMG given alone had little effect. Development of the testicular tubules was dependent upon the addition of HCG to the HMG, and the combined treatment induced a complete gonadal maturation. This LH action is presumably a direct effect on the tubules rather than indirect through Leydig cell stimulation. HMG acts synergistically with HCG in Leydig cell stimulation, and the results thus indicate a close interaction between FSH and LH on all testicular elements. No lasting effect of the long-term treatment was found. HMG has no antigenic properties in the human.

This Additional Study Showed no Long Term Reduction in Efficacy:


Smals et al. THE EFFECT OF SHORT AND LONG TERM HUMAN CHORIONIC GONADOTROPHIN (HCG) ADMINISTRATION ON PLASMA TESTOSTERONE LEVELS IN KLINEFELTER’S SYNDROME European Journal of Endocrinology, Dec 1974. Page(s): 753–764Volume/Issue: Volume 77: Issue 4

The effect of acute (1500 IU/day for 3 days) and chronic HCG administration (1500 IU, 3 times weekly) on plasma In all but one Klinefelter patient the plasma LH levels were markedly elevated even in the presence of normal testosterone levels. No significant correlation could be demonstrated between the plasma testosterone concentrations and the LH levels in the Klinefelter patients. Short term HCG administration resulted in a significant increase in the plasma testosterone levels in each of the 3 groups studied, independent of the basal value. The absolute increase in the Klinefelter patients was quantitatively comparable to that in the patients with secondary hypogonadism, but significantly lower than in the eugonadal controls. During long term HCG treatment the plasma testosterone levels definitely increased in both patient groups, but remarkably in the Klinefelter patients testosterone levels tended to decrease on continuing treatment, though in most patients testosterone levels remained higher than the pre-treatment values. The data on the effect of acute and chronic HCG administration on plasma testosterone levels in this study illustrate again that Leydig cells in Klinefelter’s syndrome still retain a functional reserve, though less than in eugonadal males.

This old study in rats probably fueled the misconception popular in other online forums about HCG desensitization, but at this relatively high dose in rat cells (IU/Kg), HCG receptor occupancy returned to normal after 120 hours. How can we extrapolate to humans?


Haour et al, HCG-Dependent Regulation of Gonadotropin Receptor Sites:


Negative control in testicular leydig cells. Molecular and Cellular Endocrinology, Volume 7, Issue 1, March 1977, Pages 17-24


Abstract

https://www.excelmale.com/video-how...-preserve-fertility-libido-and-testicle-size/

A single injection of human chorionic gonadotropin (hCG 500 IU) to prepubertal male rats increases plasma testosterone level and decreases hCG receptors in the testicular Leydig cells for more than 120 h. Injected hCG, measured in plasma using a specific radioreceptor assay for gonadotropins, is maximal at 2 h and decreases thereafter with an apparent half-life of 16 h. Plasma testosterone exhibits a rapid increase (30–40 ng/ml) within 1 h after hCG injection. A delayed paradoxical increase (20–30 ng/ml) is observed between 48 and 120 h after the injection. The number of hCG binding sites in the isolated Leydig cells membranes decreases to less than 10% of the control value within 10 h and remains almost undetectable until 96 h after hCG injection. The reappearance of the binding sites is observed around 120 h. Similar, but less pronounced effects are found after the injection of 10 IU hCG. Since receptor occupancy cannot explain such a phenomenon, it is concluded that hCG is exerting a negative control on its own receptors in the Leydig cells.

Video: How to Use hCG

 

What dose per week of HCG do you suggest for testicular size

My doc has me on 1500 IU a week (500IU 3x per week)
I feel fine. My doctor has mentioned bumping down to 750 IU would also be acceptable. But I don’t want to fix what’s not broken. But I was concerned if I was taking to most and over stimulating my leydig cells leading to HCG not being as effective eventually.
My doctor was not sure if this was a possibility. Seems like a lot of doctors are just playing a guessing game

 

L

Post in thread 'Can HCG Stop Working After Long Term Use in Men?'

May 28, 2026

Yes, I've used it for over 11 years is still working. @Nelson Vergel has used it a lot longer than me. It continues working for Nelson too

Oh awesome

I was tempted to set up an app with Lipschultz practice as I’m in Houston to go over this. But not sure if he’ll even see me since I also blast AAS

• Loubago

 

Long-Term Efficacy of Human Chorionic Gonadotropin (HCG) and the Paradox of Leydig Cell Desensitization: A Clinical Literature Review​

1. Introduction: The Clinical Role of HCG in Modern Male Hormone Management​

Human Chorionic Gonadotropin (HCG) serves a dual strategic role in contemporary male endocrinology. As an analogue to Luteinizing Hormone (LH), it is utilized both as a primary monotherapy to stimulate endogenous testosterone production and as a critical supportive agent in Testosterone Replacement Therapy (TRT) to mitigate the suppressive effects of exogenous androgens on the Hypothalamic-Pituitary-Testicular Axis (HPTA). Clinical application is typically guided by three primary objectives: the direct stimulation of intratesticular testosterone, the preservation of fertility (spermatogenesis), and the prevention of testicular atrophy.
A significant challenge in long-term patient management is the persistent clinical misconception regarding "Leydig cell desensitization." This theoretical concern—that the testes will permanently cease responding to gonadotropic signals—often acts as a barrier to optimal endocrine health, leading to reduced patient compliance and suboptimal clinical decision-making. To resolve these concerns, a rigorous distinction must be made between transient, homeostatic receptor changes and terminal clinical desensitization. This review evaluates the foundational longitudinal evidence to clarify the durability of the HCG response in human populations.

2. Longitudinal Evidence of Efficacy: The 1966 European Journal of Endocrinology Study​

To evaluate the potential for "exhaustion" of the steroidogenic pathway, researchers look to severe hypogonadotrophic hypogonadism as a clinical "stress test." These patients, characterized by persistent infantilism and a lack of endogenous LH, provide an ideal model to observe the testicular response to prolonged stimulation without the confounding variables of natural hormonal fluctuations.
In a landmark study published in the European Journal of Endocrinology (1966), researchers observed two adult men over an extended treatment period reaching up to 23 months. This study investigated the transition from HCG monotherapy to Human Menopausal Gonadotropin (HMG) monotherapy, followed by combined administration.

Table 1: Treatment Phases and Physiological Outcomes (1966 Study)​

Treatment Phase	Duration	Observed Physiological Outcomes
HCG Solo	6–23 Months	Stimulation of Leydig cells and hormone excretion; maintenance of clinical response.
HMG Solo	7–12 Months	Minimal effect on testicular maturation or tubule development when administered in isolation.
HCG + HMG Combined	9–12 Months	Induced complete gonadal maturation; HMG (FSH) and HCG (LH) acted synergistically on all testicular elements.

The synthesis of this longitudinal data provides a powerful rebuttal to advocates of "pulsatile-only" secretion who argue that constant stimulation is inherently damaging to the testis. The study demonstrated that the development of testicular tubules was actually dependent upon the addition of HCG to HMG, suggesting a direct LH effect on the tubules rather than a purely indirect effect via Leydig cell stimulation. After 23 months of high-dose administration, the researchers found no "exhaustion" or lasting negative effects, confirming that HCG maintains its potency and lacks antigenic properties in humans.

3. Comparative Efficacy in Compromised Leydig Cell Populations: The 1974 Smals et al. Analysis​

The 1974 analysis by Smals et al. is critical for understanding the "functional reserve" of the testis, particularly in genetically compromised populations like those with Klinefelter’s syndrome. This study allows us to assess whether chronic stimulation leads to desensitization in cells that are already under significant physiological stress.
In the Klinefelter’s cohort, researchers noted that endogenous LH levels were markedly elevated even when testosterone levels were within or below normal ranges. Despite this chronic exposure to high levels of endogenous LH, these Leydig cells remained responsive to exogenous HCG:

• Acute Administration (1500 IU/day for 3 days): All groups—Klinefelter’s, secondary hypogonadism, and eugonadal controls—showed a significant increase in plasma testosterone, regardless of basal values.
• Chronic Administration (1500 IU, 3x weekly):
  • Secondary Hypogonadism & Eugonadal Controls: Exhibited sustained, significant increases in plasma testosterone.
  • Klinefelter’s Syndrome: While testosterone showed a slight downward trend during continued treatment, levels in most patients remained significantly higher than their pre-treatment baseline.

This evidence refutes the theory of complete Leydig cell exhaustion. If cells that are already chronically "bathed" in high endogenous LH can still respond to exogenous HCG with a sustained increase in testosterone, the argument for rapid clinical desensitization in standard TRT patients becomes untenable.

4. Deconstructing the Rat Model Fallacy: The 1977 Haour et al. Study​

The widespread clinical anxiety regarding HCG desensitization is largely rooted in the misextrapolation of high-dose, short-term data from the 1977 Haour et al. study. Critically, this research utilized prepubertal male rats, a physiological model that bears little relevance to the adult human male on TRT.
The study involved a single massive injection of 500 IU of HCG. On a per-kilogram basis, this dose is orders of magnitude higher than standard human protocols. The researchers observed that HCG binding sites (receptors) decreased to less than 10% of control values within 10 hours and remained undetectable for 96 hours.
However, the "So What?" layer of this data reveals a misunderstood homeostatic mechanism rather than a failure of the cell. By 120 hours, the binding sites reappeared and receptor occupancy returned to normal. This indicates that the observed receptor loss was a transient "negative control" or down-regulation—a temporary "lock-out" intended to protect the cell—rather than desensitization (permanent loss of function). Furthermore, a "paradoxical increase" in testosterone was observed between 48 and 120 hours, proving the steroidogenic pathway remained functional even while receptor density was temporarily reduced.

5. Clinical Synthesis: Modern Expert Perspectives on Desensitization Mechanisms​

Expert-moderated clinical experience consistently shows a disconnect between the theoretical "receptor down-regulation" seen in extreme animal models and the long-term outcomes of human patients. In modern TRT protocols, doses such as 250–500 IU every other day (EOD) are insufficient to trigger the profound negative feedback loops observed in high-dose rat studies.

Mechanisms of Steroidogenic Desensitization​

As noted in seminal HCG modeling papers (Saez and Forest, 1979; Saal et al., 1991a), theoretical desensitization is attributed to two primary factors:

1. Estradiol-Induced Inhibition: High HCG doses can cause a disproportionate increase in estradiol, which may inhibit specific enzyme activities within the steroidogenic pathway.
2. Receptor Down-Regulation: A homeostatic reduction in receptor density in response to supra-physiological stimulation.

The Professional Stance: These mechanisms are dose-dependent and reversible. Within standard clinical norms, "desensitization" is rarely, if ever, encountered. As noted by expert moderators at ExcelMale, the ultimate clinical reality is that "most guys who stop treatment... end up no worse off than they would have been with no treatment at all," even after years of HCG use. The transient nature of receptor regulation suggests that even if a patient were to experience a slight reduction in sensitivity, a brief cessation of therapy would reset the receptor population.

6. Conclusion: A Definitive Stance on HCG Sustainability​

A comprehensive review of the clinical literature indicates that HCG is a sustainable and effective therapeutic tool for the long-term management of male hormonal health. The fear of permanent Leydig cell desensitization is unsupported by human clinical data.

Final Peer-Reviewed Perspectives:​

1. Long-Term Efficacy: Longitudinal studies confirm HCG remains effective for nearly two years of continuous use without loss of potency or the development of antigenic properties.
2. Synergistic Maturation: HCG exerts a direct effect on testicular tubules and works synergistically with HMG to maintain the health of all testicular elements.
3. Functional Reserve: Even genetically compromised Leydig cells (as in Klinefelter's syndrome) maintain a functional reserve and respond to exogenous stimulation despite high endogenous LH.
4. Reversible Regulation: Animal models demonstrating receptor loss utilize extreme doses in prepubertal subjects; even in these extreme cases, receptors recover fully within 120 hours, proving the event is transient down-regulation, not permanent failure.
5. Dosing Safety: Standard TRT-adjacent doses (250–500 IU EOD) are safely below the threshold required to induce the enzyme activity inhibition or receptor collapse seen in historical modeling studies.