Erectile Dysfunction After Semaglutide Clinical Signal and Interpretation

Study Overview and Public Reaction

In 2024, Able and colleagues published a study that quickly spread fear among patients using semaglutide (Ozempic, Wegovy) for weight loss. The researchers analyzed a large medical database called TriNetX. They compared two groups of non-diabetic men with obesity: those who received a prescription for semaglutide and those who never received it. Their finding was statistically significant. Men prescribed semaglutide appeared to have a higher risk of being diagnosed with erectile dysfunction and testosterone deficiency.

This finding made headlines. Social media amplified the message. In our clinic, patients began asking whether they should stop their medication. Some had already stopped. The fear was real and understandable. No one wants to trade weight loss for impotence.

However, a careful reading of the study reveals serious problems. The most important problem is not statistical. It is biological. The authors attempted to explain a possible mechanism for how semaglutide could cause erectile dysfunction or lower testosterone. To support their explanation, they cited an experimental paper by Li and colleagues from 2007. That paper had an attractive title: “GLP-1: a novel zinc finger protein required in somatic cells of the gonad for germ cell development.”

The abbreviation “GLP-1” in that title seemed perfect. After all, semaglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist. If GLP-1 was required for gonad development, then blocking or altering GLP-1 signaling might affect testosterone or erectile function. The logic appeared sound. But the logic was based on a mistake.

The Critical Scientific Error

The abbreviation “GLP-1” in the Li paper does not stand for glucagon-like peptide-1. It stands for GATA-like protein-1. These are two completely different molecules.

Glucagon-like peptide-1 is a hormone produced in the gut. It stimulates insulin secretion, slows gastric emptying, and reduces appetite. Semaglutide is a synthetic version of this hormone. GATA-like protein-1, on the other hand, is a nuclear protein with zinc finger domains. It plays a role in the development of gonads. It has nothing to do with appetite, insulin, or the mechanisms of semaglutide.

This confusion is documented in a scientific commentary in the International Journal of Impotence Research

The commentary, written by Dr. Selman Unal, makes a simple but important point. The original study by Able and colleagues cited a paper about GATA-like protein-1 as if it were about glucagon-like peptide-1. This is an error of abbreviation. It is the same as confusing a river with a tree because both are abbreviated “R.” The letters are identical. The meaning is not.

Why This Error Matters

Without a plausible biological mechanism, the statistical association reported by Able and colleagues becomes much weaker. Epidemiology alone cannot prove causation. To argue that semaglutide causes erectile dysfunction, one needs at least one of two things: a clear biological mechanism supported by experimental evidence, or multiple large prospective studies showing a consistent effect after controlling for confounders. Neither exists.

The Li paper does not support a mechanism. It is about a different protein. No other experimental study has shown that semaglutide damages the tissue of the penis or suppresses testosterone production in animals or humans. The known side effects of semaglutide include nausea, vomiting, diarrhea, and rarely pancreatitis. Erectile dysfunction and testosterone deficiency are not listed in the official prescribing information from the FDA or the European Medicines Agency.

Conflicting Evidence from Different Databases

The TriNetX study is not the only large database analysis on this topic. A separate study using the FDA Adverse Event Reporting System (FAERS) database examined 182 cases of male sexual dysfunction associated with GLP-1 receptor agonists. The results tell a different story.

The FAERS finding is particularly important. A reporting odds ratio below 1.0 means that sexual dysfunction was reported less frequently for GLP-1 agonists than for all other drugs in the database. If semaglutide truly caused erectile dysfunction, we would expect the opposite more reports, not fewer.

These conflicting results from large datasets tell us one thing clearly: retrospective database analyses are hypothesis-generating, not conclusive. They cannot prove causation, especially when different databases point in opposite directions.

Three Alternative Explanations for the TriNetX Findings

The statistical association observed by Able and colleagues can be explained in other ways that do not involve direct toxicity of semaglutide.

• Detection bias. Patients who start a new prescription medication visit doctors more frequently. They have blood tests. They are asked about side effects. A man who never sees a doctor may have erectile dysfunction but never receive a formal diagnosis. A man who sees a doctor every three months is more likely to have his erectile dysfunction documented in his medical record. This difference alone can create a spurious association.
• Temporary side effects mimicking sexual dysfunction. Nausea and fatigue are common during the first months of semaglutide treatment. A man who feels nauseated and exhausted is unlikely to feel interested in sex. This temporary reduction in libido is not erectile dysfunction. It does not indicate permanent damage. If patients in the database were surveyed during the first few months of treatment, their reported symptoms might be misclassified as erectile dysfunction.
• Uncontrolled confounders. The TriNetX database contains diagnostic codes but does not fully capture depression, anxiety, or the use of antidepressant medications such as SSRIs. Depression and SSRIs are both well-established causes of erectile dysfunction. If men prescribed semaglutide had higher rates of depression or SSRI use, that could explain the association without any direct effect of the drug.

These three explanations are more plausible than direct toxicity, especially given the absence of a valid biological mechanism.

The Paradox: Obesity Itself Causes Sexual Dysfunction

There is an irony in the fear surrounding semaglutide and erectile dysfunction. Obesity itself is a major cause of sexual dysfunction in both men and women.

In men with obesity, excess fat tissue contains an enzyme called aromatase. Aromatase converts testosterone into estrogen. The more fat a man has, the more testosterone is converted away. The result is lower circulating testosterone levels. At the same time, obesity promotes inflammation and vascular damage. The small arteries that supply blood to the penis become narrowed by atherosclerosis. Without adequate blood flow, an erection is impossible.

In women with obesity, similar mechanisms operate. Genital blood flow is reduced. Libido decreases. Vaginal dryness and pain during intercourse (dyspareunia) become more common. Female sexual dysfunction is underdiagnosed but highly prevalent in obese populations.

Weight loss reverses many of these changes. A man who loses 10-15% of his body weight typically sees an increase in testosterone and improvement in erectile function. A woman who loses the same amount of weight often reports improved libido and less discomfort.

This creates a paradox. Semaglutide causes weight loss. Weight loss improves sexual function. Therefore, semaglutide should improve sexual function in most patients. The TriNetX study suggesting the opposite is an outlier. It contradicts both biological logic and the clinical experience of most practitioners.

Why the GLP-1 Confusion Spread So Quickly

The error involving GLP-1 and GATA-like protein-1 is understandable. Both molecules share the same three letters. Scientists often use abbreviations without defining them in every sentence. When a reader sees “GLP-1” in a paper about gonad development, the natural assumption is that it refers to glucagon-like peptide-1. That assumption is wrong in this specific case, but it is an easy mistake to make.

However, the fact that the mistake is understandable does not make it acceptable. A scientific paper that proposes a causal link between a drug and a serious side effect must get its basic facts right. Citing a paper about one protein as evidence about a completely different protein is a fundamental error. The commentary by Dr. Selman Unal serves an important function: it corrects the record and prevents other researchers from repeating the same mistake.

What the Original Authors Did Not Do

The original study by Able and colleagues had several limitations beyond the citation error. The authors did not measure testosterone levels directly. They relied on diagnostic codes entered by physicians. A diagnostic code for testosterone deficiency may reflect a single low lab value, a clinical diagnosis without lab confirmation, or even an administrative error. The accuracy of these codes is uncertain.

The authors also did not have information about the severity of obesity, the duration of semaglutide treatment, or the dose of the drug. Patients taking semaglutide for six months may have different outcomes than patients taking it for two years. Patients on a low dose may respond differently than patients on the maximum dose. The TriNetX analysis treated all semaglutide prescriptions as equivalent.

The authors did not adjust for lifestyle factors such as diet, exercise, smoking, or alcohol use. All of these factors influence both obesity and erectile dysfunction. A man who smokes, drinks heavily, and eats a poor diet is more likely to be obese and more likely to have erectile dysfunction. If such a man is also more likely to be prescribed semaglutide, the association between the drug and erectile dysfunction could be explained entirely by his lifestyle.

Three Clinical Situations That Require Investigation

When a patient taking semaglutide reports erectile dysfunction, a systematic approach is more useful than automatic drug discontinuation.

• ED persisting beyond three months after nausea and fatigue have resolved. Temporary side effects such as nausea and fatigue typically improve within weeks to a few months. If erectile dysfunction continues after these symptoms have disappeared, the cause is unlikely to be the temporary effects of the drug. Other causes should be sought.
• Absence of morning erections. Morning erections are mediated by the autonomic nervous system and depend on intact vascular and neural function. A man who has lost his morning erections likely has an organic cause of erectile dysfunction, such as vascular disease or hypogonadism. A man who maintains morning erections but cannot achieve erections during sexual activity may have a psychogenic component.
• Confirmed hypogonadism on laboratory testing. A morning total testosterone level below 12 nmol/L (approximately 350 ng/dL) on two separate occasions confirms hypogonadism. If a patient taking semaglutide meets this criterion, the hypogonadism may be unrelated to the drug. Obesity itself is a common cause of hypogonadism. Weight loss, including weight loss with semaglutide, typically improves testosterone levels over time.

How APUMN Approaches Patients on Semaglutide

At Adult & Pediatric Urology (APUMN), we see patients who are either considering semaglutide or already taking it. Our approach is guided by the available evidence, including the correction of the GLP-1 error.

First, we do not discontinue semaglutide based on the TriNetX study alone. The study reported an association, not causation. Its proposed mechanism was based on a mistaken citation. No experimental evidence supports direct toxicity. Discontinuing an effective weight loss medication based on such weak evidence would harm patients. Obesity itself is a proven cause of erectile dysfunction, heart disease, diabetes, and cancer. The benefits of sustained weight loss far exceed the hypothetical risk suggested by a single flawed study.

Second, we evaluate sexual dysfunction independently of semaglutide use. A patient who develops erectile dysfunction while taking semaglutide may have erectile dysfunction from another cause. We take a thorough history, perform a physical examination, and order appropriate laboratory tests. These include morning total and free testosterone, estradiol, prolactin, thyroid-stimulating hormone, and vitamin D. We also assess for depression, anxiety, and medication use, especially SSRIs.

Third, we treat erectile dysfunction using standard approaches. PDE5 inhibitors such as sildenafil (Viagra) and tadalafil (Cialis) are safe and effective for most men with erectile dysfunction. There is no contraindication to using these medications together with semaglutide. For men who do not respond to PDE5 inhibitors, we offer second-line treatments including vacuum erection devices, low-intensity shockwave therapy (Li-ESWT), and intracavernosal injections of alprostadil. For men with confirmed
hypogonadism, we offer testosterone replacement therapy. None of these treatments interfere with semaglutide or with weight loss.

Fourth, we address female sexual dysfunction when present. Women taking semaglutide sometimes report reduced libido or vaginal discomfort. We evaluate nutritional status, including ferritin, zinc, and folate levels, because rapid weight loss can lead to deficiencies that affect sexual function. We assess for vaginal dryness and treat with vaginal estrogen or hyaluronic acid when appropriate. We also screen for depression and anxiety, which are common causes of low libido in both sexes.

The Importance of Not Overreacting

Medical history is full of examples where a preliminary finding caused widespread panic, only to be disproven by better research. In the 1990s, a small study suggested that calcium channel blockers increased the risk of breast cancer. Many patients stopped their blood pressure medication. Later, larger and better-controlled studies showed no association. The initial panic caused real harm.

The semaglutide and erectile dysfunction story has the potential to cause similar harm. Obesity is a chronic, progressive disease. Effective treatment requires sustained effort. A patient who stops semaglutide because of fear of erectile dysfunction may regain weight, develop diabetes, or suffer a heart attack. These outcomes are known and proven. The risk of erectile dysfunction from semaglutide is not.

What Patients Should Do

A patient taking semaglutide who develops erectile dysfunction should do three things.

• Continue the medication until a physician advises otherwise. Stopping abruptly is unnecessary and may lead to weight regain.
• Schedule an evaluation with a urologist or other sexual health specialist. The evaluation should include a history, physical examination, and laboratory testing.
• Understand that the evaluation may reveal a cause unrelated to semaglutide. Obesity, depression, low testosterone, and vascular disease are all common and treatable.

A patient considering weight loss with semaglutide should not be deterred by the TriNetX study. The study has serious limitations. Its proposed mechanism has been shown to be based on an error. Weight loss improves sexual function. Semaglutide causes weight loss. The net effect, for most patients, will be positive.

Conclusion

The scientific commentary correcting the GLP-1 confusion is an important contribution to the literature. It reminds us that citations must be accurate, that abbreviations can be misleading, and that statistical associations are not proof of causation.

The original study by Able and colleagues raised an interesting question. Can semaglutide affect erectile function or testosterone levels? The answer remains unknown. The study did not prove that it can. The proposed mechanism was based on a mistaken citation. No experimental evidence supports direct toxicity. Alternative explanations for the findings are more plausible.

What is known is this. Obesity causes erectile dysfunction in men and female sexual dysfunction in women. Weight loss improves sexual function in both sexes. Semaglutide is an effective tool for achieving weight loss. Patients should not abandon effective treatment based on unproven and mechanistically flawed claims.

At APUMN, we will continue to monitor the evidence. If future, well-designed studies show a genuine risk, we will update our recommendations. For now, the evidence does not support discontinuing semaglutide to prevent erectile dysfunction. Patients who develop erectile dysfunction while taking semaglutide deserve a thorough evaluation and standard treatment, not automatic drug withdrawal. The goal is to help patients achieve both a healthy weight and a satisfying sex life. These goals are not in conflict. With careful management, most patients can achieve both.

Author

Gregory S. Parries, M.D., PhD