TRT Clinic Revenue Loop

Testosterone converts into estrogen inside your body, and that conversion is not a side effect to be corrected. It is part of how testosterone works. Understanding that one fact changes how you read almost every protocol coming out of cash-pay TRT clinics right now.

Here is the full chain first, so you have the map.

When you inject or apply testosterone, an enzyme called aromatase, which sits in fat tissue and other cells throughout your body, converts a portion of that testosterone into estradiol, which is the primary form of estrogen in men. That estradiol then travels to your liver and signals it to convert growth hormone into something called IGF-1, which is short for insulin-like growth factor 1 and is the molecule your body uses to build and repair tissue. So the pathway runs: testosterone, to estrogen, to IGF-1. They are connected. You cannot pull one piece out without affecting the others.

Now zoom into what happens when a clinic interrupts that chain.

An aromatase inhibitor, or AI, is a drug that blocks the aromatase enzyme so that testosterone cannot convert into estrogen. The idea behind prescribing one during TRT is that elevated estrogen causes side effects like water retention or mood changes, so you suppress it. That logic is not entirely wrong. There are men who aromatize heavily, develop symptoms, and see genuine relief from estrogen management. That part is real.

What clinics often skip is what happens downstream when you do not just lower estrogen but crash it.

The liver needs estrogen to efficiently convert growth hormone into IGF-1. Think of estrogen here the way you would think of a key in an ignition. Growth hormone is the fuel in the tank, but without the key turning, the engine does not run. When you remove the estrogen signal, the liver loses the driver for that conversion and IGF-1 production collapses.

A 2017 randomized controlled trial by Dias and colleagues tested exactly this in 37 men over age 65. One group received transdermal testosterone gel. Another group received an aromatase inhibitor. The testosterone group saw their IGF-1 rise by 15.3 nanograms per milliliter over the course of the study, because the testosterone was aromatizing into estrogen and that estrogen was doing its job in the liver. The AI group saw a rise of 0.3 nanograms per milliliter. Same study population, same baseline, same timeframe. The only variable was whether estrogen was allowed to do its work.

0.3 is not a modest benefit. It is essentially a flat line.

So if you are on testosterone and an AI, your clinic has likely already observed this outcome in your bloodwork, even if they did not frame it that way. Your IGF-1 is probably low. And if your clinic then suggested adding IGF-1 as a separate product, you are looking at a protocol that created the deficiency in step two and is now selling you the fix in step three.

The FDA-approved version of IGF-1 is a drug called mecasermin, sold under the brand name Increlex, and it was approved specifically for children with a condition called growth hormone insensitivity, sometimes called Laron syndrome, where the body cannot respond to growth hormone at all and therefore cannot produce IGF-1 through any normal mechanism. That condition affects somewhere between 350 and 500 people worldwide. It is a rare genetic disorder, not a lab value that dropped because someone was taking anastrozole.

The version being sold in cash-pay clinics is not the approved pediatric formulation being used for its approved purpose. It is a peptide being administered off-label to men whose IGF-1 is low for a reason that was introduced by the same clinic.

What makes this pattern particularly worth understanding is that AI use is not even standard of care. A 2020 survey by Butaney and colleagues of nearly 500 physicians who are members of the International Society for Sexual Medicine found that 69.4 percent of them prescribed AIs for symptomatic elevated estrogen during TRT, despite the fact that neither the Endocrine Society nor the American Urological Association recommends routine AI use for estradiol management in their formal guidelines. That gap between what guidelines say and what prescribers do is where the revenue loop lives.

If you are currently on testosterone and an AI, the most direct thing you can do is get your IGF-1 level checked before agreeing to any additional peptide or hormone product. If your IGF-1 is low, the first question to ask is not how to supplement it back up, but whether your estrogen has been suppressed to the point where the liver pathway cannot function, and whether reducing or eliminating the AI would let your body recover that production on its own.

Some men do need estrogen management during TRT. Some men aromatize to a degree that creates real problems and benefit from a conservative, carefully dosed AI. The distinction is between using a drug to manage a genuine symptom at a dose that maintains estrogen in a functional range, versus using a drug to suppress estrogen below the floor and then charging for the downstream consequences.

Most of the body's hormone systems are not separate dials you can tune independently. They are one connected system, and when a clinic treats them like isolated levers, they are either not seeing the full picture or they are counting on you not to.

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References

1. **Dias JP et al.** "Effects of transdermal testosterone gel or an aromatase inhibitor on serum concentration and pulsatility of growth hormone in older men." *Metabolism*, 2017; 69:143-147. PMID: 28285644. RCT, 37 men aged 65+. Testosterone group: +15.3 ng/mL IGF-1. AI group: +0.3 ng/mL.
2. **Butaney M et al.** "Treatment of estrogen levels in the management of hypogonadism: An anonymous survey of ISSM members." *Urology*, 2020; 141:68-74. PMID: 32045591. 69.4% of 489 surveyed physicians prescribed AIs for symptomatic elevated estrogen.
3. **FDA Label (NDA 021839):** Increlex (mecasermin) approved for growth failure in children with severe primary IGF-1 deficiency. Orphan drug. Pediatric only.
4. **Orphanet:** Laron syndrome affects approximately 350-500 individuals worldwide. Prevalence: 1-9 per 1,000,000.
5. **AUA 2018 Guideline** (Mulhall JP et al., PMID: 29601923) and **Endocrine Society 2018** (Bhasin S et al., PMID: 29562364): Neither endorses routine AI use for estradiol management during TRT.

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