How restoring your own testosterone differs from replacing it, and why that matters if you want kids.
TRT supplies testosterone from outside the body, which tells the brain to stop sending the signals (LH and FSH) the testes need to make sperm. Enclomiphene works upstream, prompting the body to raise its testosterone. In two phase III trials, it preserved sperm counts while testosterone gel lowered them. But enclomiphene is not FDA-approved, long-term safety is unknown, and regulators flagged blood clot risk. Your doctor can help you weigh both.
Your testosterone is low, and you may want kids someday. That raises a fair question: will treatment affect your fertility? At King’s Pharmacy and Compounding Center, a compounding pharmacy in Irvine, CA, men ask us about enclomiphene vs. TRT more and more.
The answer matters because the two approaches work in very different ways. Testosterone replacement therapy (TRT) adds testosterone from outside the body. Enclomiphene aims to restore the body’s own production by changing the signals between the brain and the testes.
That difference can have a real effect on sperm counts. It is also why the choice deserves a careful talk with your doctor, not a quick decision. Below, we explain how each option works, what the research shows, the regulatory gaps, and what to ask at your next appointment.
One note up front: we are pharmacists, not your prescriber. Neither option is right for everyone. Only your doctor can diagnose low testosterone and recommend treatment.
How TRT Works and Why It Can Lower Sperm Counts
TRT raises testosterone by supplying it directly, through gels, injections, or pellets. The brain senses those higher levels and slows its release of LH and FSH, the two hormones that tell the testes to make testosterone and sperm. With less signaling, sperm production often drops, sometimes sharply.
Your body runs testosterone on a feedback loop. The hypothalamus and pituitary gland in the brain watch hormone levels and adjust their signals to keep things in balance. When testosterone arrives from outside, the loop reads it as “enough” and turns down its output.
That helps with symptoms, but the testes depend on those signals. Inside the testes, LH drives testosterone production, while FSH supports sperm production. When both fall, the testes make less of each, even when blood testosterone looks normal on a lab report.
For many men, this is not a problem. If you are done having children or never plan to, TRT is a well-studied, FDA-approved therapy with decades of clinical use. But if fertility is a near-term goal, raise this effect with your doctor before you start.
TRT also has its own monitoring needs. A retrospective Baylor study of men on different testosterone forms found high red blood cell levels (erythrocytosis) were more common with injections than with pellets or gels. Topical gels also carry an FDA boxed warning about passing testosterone to children through skin contact.
“TRT can bring testosterone levels back to normal while sending sperm production in the opposite direction.”
How Enclomiphene Works: Signaling Your Body to Make Its Own Testosterone
Enclomiphene blocks estrogen receptors in the hypothalamus. That quiets the brain’s normal brake on hormone production, so the pituitary releases more LH and FSH. LH prompts the testes to make more testosterone, and FSH supports sperm production. The goal is to restore your own output rather than replace it.
Estrogen plays a part in men’s hormone feedback, too. When the brain senses estrogen, it eases off LH and FSH. By blocking that message at the receptor, enclomiphene encourages the brain to keep the signals flowing, as described in this overview of enclomiphene’s mechanism, efficacy, and safety.
You may have heard of clomiphene citrate, a related drug. Clomiphene is a mix of two forms: roughly 62% enclomiphene and 38% zuclomiphene. Zuclomiphene has weak estrogen-like effects and has been linked in reviews to side effects such as mood changes. Enclomiphene is the isolated form, described as a pure estrogen receptor blocker.
This approach only works if the testes can still respond. It is generally discussed for secondary hypogonadism, where the problem starts in the brain’s signaling rather than in the testes. Your doctor can help determine which type you have.
It also helps to know what enclomiphene is not. It is not testosterone, and it does not directly add a hormone to your body. Instead, it works on the signals your body already uses, which is the key difference in any enclomiphene vs. TRT comparison.
Enclomiphene vs. TRT: What the Research Shows
The best-known head-to-head data come from two phase III trials published in BJU International in 2015. In overweight men with secondary hypogonadism, enclomiphene restored testosterone to normal and maintained sperm concentration. Topical testosterone gel also restored testosterone but markedly reduced sperm concentration.
Those results, reported by Kim and colleagues, support the core idea. Raising testosterone from the inside can spare sperm production, while replacing it from the outside tends to suppress it. The trials were randomized and double-blind, which adds weight to the findings.
Still, the evidence has clear limits. The studies tracked hormone levels and sperm counts over a fairly short period. A 2024 review by Saffati and colleagues noted reported side effects such as headache, nausea, and mood changes; short-term safety similar to TRT (including a risk of blood clots, called venous thromboembolism or VTE); and no established long-term safety.
Regulators have weighed in, too. In 2015, the FDA issued a complete response letter on enclomiphene, saying the phase III design was no longer adequate to show clinical benefit, and it asked for more studies. In 2018, the European Medicines Agency refused marketing authorization for EnCyzix, citing VTE risk and noting the trials did not measure outcomes like libido, erectile function, or bone strength.
So what does the enclomiphene vs. TRT research mean for you? It suggests a real fertility advantage for enclomiphene in the right patient. It also leaves open questions about long-term risks and symptom relief that only more studies can answer.
“Enclomiphene’s fertility data are promising, but short-term results are not the same as proven long-term safety.”
Enclomiphene vs. TRT Side by Side
Here is a simple comparison of enclomiphene vs. TRT. Individual results vary, and your doctor will tailor any plan to you.
- How it’s taken: TRT comes as gels, injections, or implanted pellets. Enclomiphene is taken by mouth when prescribed and compounded.
- Effect on sperm: TRT often suppresses sperm production by lowering LH and FSH. Enclomiphene maintained sperm concentration in short-term phase III trials.
- Monitoring: Both call for regular lab work. TRT monitoring often includes testosterone and red blood cell levels. With enclomiphene, doctors track hormone levels and may order semen testing if fertility is the goal.
- Regulatory status: TRT products are FDA-approved for men with confirmed testosterone deficiency. No FDA-approved enclomiphene product exists in the US, and the EU refused its marketing authorization.
Neither option is clearly superior. TRT has a long track record and approved products. Enclomiphene may suit a narrower group of men whose top priority is protecting fertility, with less certainty about long-term effects.
Which option might fit you best? Questions for Your Doctor
The right choice depends on your diagnosis, your health history, and your family plans. A good first step is confirming the diagnosis. The American Urological Association guideline says testosterone deficiency requires both low lab values and related symptoms, since symptoms alone are not specific.
If you are still sorting out symptoms, our post on the signs of low testosterone in men is a helpful starting point. Then bring these questions to your appointment:
- Is my low testosterone primary (testicular) or secondary (brain signaling)?
- How soon do I hope to have children, and how does that change my options?
- What does the evidence on enclomiphene vs. TRT mean for someone like me?
- What are the known risks, including blood clots, and what is still unknown?
- What lab work or semen testing will we use to track progress?
- If I begin TRT now, what will occur if I later wish to attempt to conceive?
Bring a list of your current medications and supplements, too. Your doctor needs the full picture to judge safety. For a broader look at hormone treatment for men, see our guide to BHRT for men and andropause.
Where a Compounding Pharmacy Fits In
If your doctor decides enclomiphene is appropriate, a compounding pharmacy would prepare it, because there is no FDA-approved enclomiphene product in the US. Compounded medications are not FDA-approved, and compounding never replaces your physician’s care. Every compounded medication starts with a valid prescription.
Enclomiphene citrate sits in Category 1 of the FDA’s interim 503A bulk drug substances categories. That means it is under evaluation, and pharmacies may compound it while the review is pending. The FDA’s Pharmacy Compounding Advisory Committee voted in 2022 against recommending it for the final list. The vote was not binding, but its status could change.
At King’s Pharmacy, our role is to prepare what your prescriber orders, carefully and accurately. We are NABP accredited, a PCCA member, and licensed in California and 12 other states. We work closely with doctors through our prescriber services, and you can learn more about our men’s health services.
Our pharmacists are also here to listen. We can review your other medications for possible interactions, explain how to store your prescription, and talk through side effects to watch for. If something feels off, we will encourage you to contact your doctor promptly.
The Bottom Line
The enclomiphene vs. TRT decision comes down to how each one treats your body’s own signals. TRT replaces testosterone and often lowers sperm production. Enclomiphene prompts your body to make more of its own and preserves sperm counts in short-term trials. However, it is not FDA-approved, and its long-term safety is still unknown.
If children are part of your plans, raise fertility before you start any testosterone treatment, not after. An honest talk with your doctor about goals, timing, and risk is the most important step.
Have questions about whether a compounded medication is right for you? Talk to your prescribing physician, then connect with the pharmacists at King’s Pharmacy and Compounding Center in Irvine, CA to get started.
Request a Refill or Contact King’s Pharmacy at 949.387.0780.
Frequently Asked Questions
Does TRT make you infertile?
TRT can sharply lower sperm production because it suppresses LH and FSH, the hormones the testes need to make sperm. Sperm counts often recover after stopping, but recovery time varies and is not guaranteed. If you want children, talk with your doctor before starting TRT.
Is enclomiphene FDA-approved?
No. There is no FDA-approved enclomiphene product in the US. The FDA issued a complete response letter in 2015 asking for more studies, and the EU refused marketing authorization in 2018. Doctors may prescribe it as a compounded medication, which the FDA has not approved.
Is enclomiphene the same as clomiphene?
Not exactly. Clomiphene citrate is a mix of about 62% enclomiphene and 38% zuclomiphene. Enclomiphene is the isolated form and acts as a pure estrogen receptor blocker, while zuclomiphene has weak estrogen-like activity linked to some side effects.
What are the side effects of enclomiphene?
Reported side effects include headache, nausea, and mood changes. Reviews describe short-term safety as similar to TRT, including a risk of blood clots (VTE), which European regulators flagged. Long-term safety has not been established, so ongoing monitoring with your doctor matters.
Can a compounding pharmacy fill an enclomiphene prescription?
A licensed 503A compounding pharmacy may prepare enclomiphene with a valid prescription while the FDA’s review of the substance is pending. That status could change. Your doctor decides whether it is appropriate, and your pharmacist can answer questions about the prepared medication.
