Erectile dysfunction as an early warning: blood flow, not hormones

The Short Version

Most men assume erection trouble means low testosterone. Two urologists say that is rarely the cause: Michael Eisenberg puts hormonal cases at under 10 percent and probably around 5, and Rena Malik puts them at about 3 percent [1][2]. Both say the usual cause is blood flow, and because the arteries of the penis are only about a millimeter wide, they can show vascular disease before the larger arteries of the heart do [1]. Malik cites a figure that about 15 percent of men who develop erectile dysfunction have a cardiovascular event within seven years [2]. In younger men she more often finds a tense pelvic floor, long hours of sitting and anxiety, and physical therapist Kelly Starrett and hormone physician Kyle Gillett describe the movement and lifestyle side of the same picture [2][3][4]. The practical conclusion is shared by all four: treat the symptom as a reason to get checked and to fix what feeds it, even though the pills work [1][2][4]. This article reports what these clinicians said; any man with these symptoms should see a doctor.

Table of contents

What They Said

Michael Eisenberg: a one-millimeter artery

Eisenberg is a Stanford urologist, and erectile dysfunction is the condition he sees most [1]. He gives its scale first. Over half of men past 40 have some trouble with erections, and about 15 to 20 percent of men under 40 [1]. It was once thought to be primarily psychological. That view is decades old, he says: "now we know that most of them are organic so it's actually a blood flow issue" [1].

The causes he lists are the ones that damage blood vessels anywhere in the body: high blood pressure, diabetes, and, more broadly, lifestyle and obesity [1]. Then he explains why the penis can be first to show it. The penile arteries are about one millimeter across, while those of the heart and brain are much larger, and a small vessel is easier to block than a large one. That is why, he says, some studies support the idea that erection trouble is "sort of an early marker for vascular disease" [1].

On hormones he is specific. Endocrine disorders are a fairly small share: "it's probably less than 10% probably around 5% or so" [1]. Andrew Huberman, the host, flags this as a surprise to many men, since the common belief behind much of the interest in testosterone therapy is that erection problems mean low testosterone [1]. Eisenberg names one more common cause that is neither vascular disease nor hormones: treatment for pelvic cancers, such as prostate, bladder or colorectal cancer, which can affect the nerves and vessels of the pelvis [1].

What he does with a new patient follows from the artery argument. Huberman asks whether a man whose erections are fixed by a pill still needs a conversation about the rest of his blood vessels. Eisenberg's answer: "Well, I think they should be screened." [1] Sometimes, he says, he is the first doctor the man has seen in a long time, and he sends patients to primary care to be checked for blood pressure, lipid levels and fasting blood glucose [1]. He adds that the ideal patient with perfect body weight and nothing else going on is rare, so there is usually something to improve, and that improving it can sometimes improve the erections [1]. He frames it calmly: "I try not to be alarmist about this" [1].

He is equally clear that the condition is treatable at every level. First come the PDE5 inhibitors, sildenafil (Viagra), tadalafil (Cialis), avanafil and vardenafil, which help 60 to 70 percent of men; they are vasodilators, so the side effects are headache, flushing, back aches, indigestion and nasal congestion [1]. Next are urethral suppositories or gels, then injections of vasodilators into the penis, which are 80 to 90 percent effective but which many men give up, and finally a surgically implanted prosthesis [1]. His reassurance to patients is "as long as you have a penis we can always make it hard." [1] He also notes that erections during sleep are normal and a sign of healthy function [1].

Two other points of his bear on blood flow. The pelvic floor muscles support the penis, prostate, bladder and rectum, and therapy for them has to be tailored: some men need strengthening, for example after prostate cancer surgery, while anxious, tense men may need to learn to relax those muscles, so Kegels are not a blanket prescription [1]. And cycling can matter: pressure from the nose of the saddle can compress the arteries and nerves supplying the penis, causing numbness or erection problems in perhaps 20 to 30 percent of riders [1].

Rena Malik: hormones are the misconception, and young men are a different case

Malik, a urologist and pelvic surgeon, starts from the same correction. A central misconception, she says, is that hormones cause most sexual dysfunction [2]. Her number for erections is lower than Eisenberg's: "there's only 3% of erectile dysfunction that's related to hormones" [2]. The summary of her conversation gives the range as about 3 percent and up to 6 [2]. She draws a line that explains the confusion. Testosterone is the main hormone for desire, in both sexes; desire, wanting sex, is a separate thing from arousal, the body's response [2]. A man can have a hormone problem that lowers his interest without it being what stops the erection.

Her figures for scale match Eisenberg's: about 52 percent of men over 40 have some erectile dysfunction, rising roughly with age, and most of it is vascular [2]. She assesses blood flow first through a man's other conditions. The most common are high blood pressure, diabetes, heart disease and smoking, and in her words "all of those things will affect blood flow to the genitals" [2]. If needed, a Doppler ultrasound can look at the vessels directly [2]. Nicotine, from smoking or vaping, is a vasoconstrictor that works against erections [2].

She gives the mechanism in a few steps. Erection is driven by the parasympathetic nervous system through nitric oxide, released in response to a stimulus. Nitric oxide sets off a cascade that produces cGMP, which drives the erection and is broken down by an enzyme, phosphodiesterase. PDE5 inhibitors slow that breakdown [2]. In studies they produce erections sufficient for intercourse in about 60 to 70 percent of men, and she says failures often reflect wrong dosing, poor use, or anxiety and stress [2].

Her most distinctive contribution concerns men in their 20s and 30s. Asked why so many of them write in about erection problems, she answers from her clinic: "they very often have pelvic floor dysfunction" [2]. She links it to stress and to sitting, especially during the pandemic, when people sat at home computers for months. Exercise does not cancel it: "exercising one hour is not going to offset the day full of sitting" [2]. She calls this her theory of the more common cause in that group, and adds that performance anxiety often compounds it [2].

The pelvic floor, as she describes it, is a bowl of muscles that holds up the pelvic organs. Like any muscle worked without rest it can become contracted, short and tight, often without the person knowing [2]. The link to erections is anatomical: the pudendal nerve and artery run through the pelvic floor, so dysfunction there can reduce blood flow and inflame nerves [2]. A tight pelvic floor can also show up as urinary urgency or frequency, pain with erections or ejaculation, constipation and back pain [2]. Most people cannot tell whether theirs is tight or weak, which is why she sends them for an exam; Kegels strengthen, and overdoing them can create a tight, dysfunctional pelvic floor [2]. Huberman reports that trying Kegels gave him painful urination that stopped when he quit them [2].

She also supplies the test that separates body from mind. A key question for any man is whether he gets erections at night, which shows whether the organ itself works apart from performance anxiety [2]. Anxiety can build its own loop, in which one poor experience leads to worry and more failures, and she agrees with the saying in her field that "the brain is the most powerful organ for sex." [2]

Finally she gives the statistic that turns a bedroom problem into a medical one: about 15 percent of men who develop erectile dysfunction have a cardiovascular event within seven years, which is why she says it warrants a cardiovascular checkup [2]. Her strongest advice is lifestyle before pills: manage blood pressure and diabetes, eat a Mediterranean-style diet, which she calls the best studied in sexual dysfunction, do both aerobic and resistance training, sleep well, and quit smoking and vaping [2]. She has seen how fast men can change when it counts: those who must lower their blood sugar marker before penile implant surgery change their habits remarkably quickly [2].

Kelly Starrett: hips, posture and "this thing called blood flow"

Starrett is a doctor of physical therapy who coaches athletes, and he comes at the pelvic floor through performance [3]. He points to urinary leakage during heavy lifts or jump rope as a sign that the body cannot manage pressure in the abdomen, often tied to a forward-tilted pelvis that switches off the glutes and pelvic floor [3]. He describes the pelvic floor in plain terms as everything between the pubic bone, the tailbone and the two sit bones [3].

His story about erections is a single case, told for effect. A well-known friend was filming a television show, and Starrett worked on the internal rotation and flexion of the man's hip. That night he got a text from the friend asking what had happened to his erections, which had improved dramatically. Starrett's reply was "well, there's this thing called blood flow." [3] The summary of the conversation describes the improvement as likely due to better blood flow [3]. It is one anecdote, from a therapist, about one man.

Huberman adds his own experience in this conversation. Years earlier he had pain in the prostate area despite a normal PSA test. He took Starrett's men's pelvic floor course, changed how he sat, moved to a sit-stand desk, wore flat shoes and did full-range glute ham raises, and it resolved [3]. He repeats the warning he took from the urologists: for a man with a tight pelvic floor, Kegels can make urinary and erectile problems worse, because "you need to learn to relax your pelvic floor" [3].

Starrett's practical method is gentle. Following the teacher Jill Miller, he suggests mobilizing the abdomen and pelvic floor at home with a soft ball, avoiding the openings; anything painful under compression is a place to breathe, contract and relax [3]. His wider prescriptions are about not sitting in one shape all day: twenty to thirty minutes on the floor each evening in varied positions, a work setup that invites movement, and restoring hip extension, which he finds eroded in almost everyone [3]. On how hard to train he says "let's be consistent before we're heroic." [3]

Kyle Gillett: the canary, and the limits of the hormone answer

Gillett's field is hormone optimization, which makes his agreement notable. Describing the patient who mentions low libido, a little erectile dysfunction and chest pressure only as he is leaving the room, he says the symptoms can be related: "erectile dysfunction is known as the canary in the coal mine" [4]. The plaque that causes erection problems can also build up in the coronary arteries [4].

He still orders labs every time, because two men with the same symptoms can have very high or very low testosterone [4]. And he asks whether the problem is situational. He describes a rarely ordered test of erections during sleep, which shows normal nighttime erections in about 90 percent of cases, pointing to a situational cause [4].

His list of things that work against erections is mostly vascular and mechanical. Nicotine, especially smoked, is a vasoconstrictor linked to cardiovascular and microvascular disease [4]. Long periods on a bike seat put pressure on the perineum and can weaken the pelvic floor [4]. Heavy leg training done well strengthens the pelvic floor and done poorly weakens it [4]. On Kegels he is blunt: "don't just take the advice, do kegels and you'll be okay" [4]. He adds, "That is not near enough." [4] Huberman supplies the reason in the same exchange: the erection response is parasympathetic, a relaxation response, so excessive contraction can limit blood flow [4].

He also describes a hormonal route that has nothing to do with testosterone therapy. Prolactin rises sharply after ejaculation and suppresses the hormones that drive testosterone, so in his view daily or more than daily masturbation would be very detrimental hormonally, and with pornography likely worse [4]. This is his opinion as stated; Malik's position is that masturbation to pornography is fine for people whose lives and relationships are going well, with problematic use identified in about 4 percent of people in studies [2].

On medication he is enthusiastic: "Tadalophil is a very underrated medication." [4] At 2.5 to 5 milligrams a day he uses it for prostate health, and says it roughly halves nighttime urination, which improves sleep [4]. For young men with testosterone in the normal range, he says the benefit of testosterone therapy almost never outweighs the harm [4].

Where They Agree, and Where They Don't

Hormones are a small part. Eisenberg says around 5 percent and under 10; Malik says about 3 and up to 6 [1][2]. The exact figure differs, the conclusion does not. Gillett, whose practice is hormones, treats erection problems first as a vascular warning [4].

It is a signal about the heart and vessels. Eisenberg gives the anatomical reason, Malik the seven-year figure, Gillett the canary [1][2][4]. All three send the man for a wider check.

Kegels are not the answer by default. Eisenberg, Malik, Gillett, Starrett and Huberman all say the same thing from different chairs: some men need to strengthen and many need to relax, and only an assessment tells which [1][2][3][4].

Lifestyle comes first, and the drugs are still good. Malik says build on exercise, diet, sleep and not smoking before reaching for pills or supplements [2]. Eisenberg wants men to take ownership of their health and reminds them that there are terrific medications for those in whom lifestyle is not enough [1].

They differ on how much is physical. Eisenberg says most cases are organic [1]. Gillett says the nighttime test is normal in about 90 percent of cases, pointing to a situational cause [4]. These statements pull in different directions, and the sources do not reconcile them. Part of the gap may be who is being tested: Eisenberg is speaking of all men with the condition, weighted toward those over 40 with vascular risk, while a hormone clinic sees many younger men. Malik's account sits between the two. In older men she finds vascular disease; in men in their 20s and 30s she finds pelvic floor tension and anxiety, which are neither blocked arteries nor low hormones [2].

They differ on cycling. Eisenberg estimates 20 to 30 percent of riders are susceptible to numbness or dysfunction and advises standing up periodically, a professional saddle fit, and changing saddle or style if symptoms appear [1]. Malik cites genital numbness in up to 50 percent of high-volume cyclists and recommends a wider, noseless seat, warning that cutout seats may raise pressure around the opening; she also notes one study of sports club members that found similar rates of erectile dysfunction among cyclists, runners and swimmers, and does not want people to stop riding [2]. Gillett simply lists long rides among the things to limit [4].

They differ on heavy lifting. Huberman says many people who squat and deadlift heavy, or who do a lot of abdominal work, report erection problems or pain, which he reads as over-contraction [2]. Gillett says heavy leg training done well strengthens the pelvic floor [4]. Malik's note on breathing may connect them: the pelvic floor relaxes on the inhale and contracts on the exhale, and holding the breath during lifts adds strain [2].

They give different numbers for tadalafil. Eisenberg's conversation describes a half-life of roughly 20 hours; Malik says 36 [1][2]. Both describe it as long-acting, and neither figure changes the advice.

Why It Works

Small vessels fail first. A one-millimeter artery narrows to the point of trouble sooner than a large coronary artery does, so the same disease process announces itself in the penis earlier [1]. Gillett's version is that the plaque is the same plaque [4].

Erection is a blood flow event run by a relaxation signal. Nitric oxide, released under parasympathetic control, starts the chain that fills the tissue [2]. Anything that narrows vessels (nicotine, high blood pressure, diabetes) or blocks the signal (anxiety, a clenched pelvic floor) interferes at a different point of the same pathway [2][4]. The pills act late in that chain by slowing the breakdown of cGMP, which is why they can restore erections without touching the cause [2].

The supply line runs through the pelvic floor. The pudendal artery and nerve pass through these muscles, so chronic tension there can reduce flow and irritate nerves [2]. A saddle nose compresses the same structures from outside [1][2]. Starrett's hip work and Huberman's changes to sitting are attempts to take pressure off the same region [3].

Sitting is its own exposure. Malik's point is that a day of sitting is not undone by an hour of training [2]. Starrett's is that a body adapts to the few positions it is kept in [3]. Eisenberg notes that more daily steps are associated with higher testosterone across body weight categories, and Malik recommends walking more and a standing desk [1][2].

Anxiety feeds itself. One failure produces worry, worry produces the next failure [2]. Daily low-dose tadalafil helps here, Malik says, because the man does not have to remember a pill before sex: "It's always on board." [2]

Where It Applies, and Where It Doesn't

The vascular warning fits best for men with risk factors and gradual onset. High blood pressure, diabetes, smoking, excess weight and age over 40 are where Eisenberg and Malik place most cases [1][2]. The sources do not say that every erection problem predicts heart disease, and Eisenberg takes care not to be alarmist [1].

In younger men, look at the pelvic floor, sitting and anxiety. That is Malik's clinical experience, offered as her theory [2]. Normal nighttime erections suggest the plumbing works [2][4].

Hormones still deserve a test. Three to ten percent is not zero, low desire is a different complaint from poor erections, and Gillett orders labs for everyone [1][2][4]. What the sources argue against is starting with testosterone. Huberman's view in the Eisenberg conversation is that testosterone therapy should not be the entry point before sleep, exercise, alcohol, smoking and body weight are addressed, and Eisenberg notes that it shuts down sperm production [1].

Other causes exist. Pelvic cancer treatment is a common one [1]. Medication can be another: Malik notes that SSRIs affect sexual function and that erectile dysfunction and depression are intertwined [2]. Finasteride can cause sexual side effects that in some men persist [1].

The movement evidence is thin. Starrett's account is one friend's text message [3]. It supports trying a pelvic floor assessment; it does not show that hip mobility treats erectile dysfunction.

Supplements are a maybe. Malik says L-citrulline has reasonable data, that the industry is unregulated, and that anything which works instantly probably contains a hidden drug [2].

An erection lasting more than four hours without arousal is an emergency. Malik says to go to an emergency room; it is rare with pills and more common with injections [2].

What To Do With It

1. See a doctor and ask for the vascular basics. Blood pressure, lipids and fasting glucose are what Eisenberg has patients screened for [1]. Do this even if a pill has fixed the symptom.

2. Notice whether you get erections during sleep or on waking. If you do, the organ works, and the cause is more likely situational, anxious or muscular [2][4].

3. Get hormones measured, and do not start there. Have testosterone checked with the rest of the labs [4]. Address sleep, weight, alcohol and smoking before considering testosterone therapy [1].

4. Stop nicotine in every form. Smoking and vaping both constrict vessels [2][4].

5. Sit less across the whole day. Walk more, use a standing desk, and spend time on the floor in the evening; an hour in the gym does not offset the rest [2][3].

6. Do not start Kegels on your own. Ask a urologist or a pelvic floor physical therapist with experience in men whether your pelvic floor is tight or weak. If any exercise brings on symptoms, stop [2][4].

7. Breathe when you lift. Exhale on effort, and do not hold your breath through crunches or heavy sets [2].

8. If you cycle and feel numbness, change something. Stand up in the saddle regularly, get a professional fit, or try a wider or noseless seat [1][2].

9. Eat and train for your arteries. A Mediterranean-style diet, aerobic and resistance exercise, good sleep, and control of blood pressure and blood sugar are Malik's foundation [2].

10. Ask about medication without embarrassment. PDE5 inhibitors help most men, daily low-dose tadalafil is an option your doctor can discuss, and there are further steps if pills fail [1][2].

Sources

1. Dr. Michael Eisenberg: Improving Male Sexual Health, Function & Fertility · Huberman Lab
2. Dr. Rena Malik: Improving Sexual & Urological Health in Males and Females***** · Huberman Lab
3. Dr. Kelly Starrett: How to Improve Your Mobility, Posture & Flexibility · Huberman Lab
4. Dr. Kyle Gillett: Tools for Hormone Optimization in Males · Huberman Lab