Stirling Cooper's testosterone warning signs, fact-checked

What did @stirlingcooperofficial actually say?

The claim is simple and blunt: if you're not "waking up in the morning with a bone," there's "a large possibility" you have low testosterone, and you should get it checked. Credit where it's due, the video ends with sensible advice to see a doctor. But the path to that advice runs through a pretty significant oversimplification that's worth unpacking.

Morning erections, clinically called nocturnal penile tumescence (NPT), are real physiological events. They happen during REM sleep and are influenced by hormones, neurological function, and vascular health. Stirling Cooper is pointing at a real phenomenon. The problem is in how directly he ties the absence of morning erections to low testosterone specifically.

Does the science back this up?

Partly, but the relationship is more complicated than this video lets on. Testosterone does play a role in NPT, but it is one factor among several, and not necessarily the most important one.

A 2009 study by Schiavi and Rehman in the Journal of Sex and Marital Therapy established that androgen levels correlate with NPT frequency and rigidity in healthy men. More directly, Jain et al. (2000) in Journal of Urology found that testosterone replacement in hypogonadal men improved NPT measurements. So the hormone-erection link is real and documented.

However, Shamloul and Ghanem (2013) in The Lancet reviewed erectile dysfunction broadly and identified cardiovascular disease, diabetes, neurological disorders, medications (especially antidepressants and antihypertensives), sleep disorders, and psychological stress as major drivers of impaired NPT and ED, often independent of testosterone levels. You can have perfectly normal testosterone and still have absent morning erections due to obstructive sleep apnea alone.

What did they get wrong (or right)?

The creator got one thing meaningfully right: absent morning erections can be a symptom worth investigating. That part holds up. Telling men to "get it checked" is genuinely good public health messaging, even if the framing is imprecise.

What they got wrong is the implied causation. Saying there's "a large possibility" of low testosterone if you're not waking up with an erection overstates how specifically this symptom points to hypogonadism. The American Urological Association's 2018 guidelines on testosterone deficiency list morning erections as one symptom among many, not a standalone diagnostic indicator. A single symptom is not a diagnosis.

The video also ignores age. NPT frequency and rigidity decline naturally with age even when testosterone is in a completely normal range, as documented by Schiavi et al. (1990) in Psychosomatic Medicine. A 55-year-old man having fewer morning erections than he did at 25 is not automatically hypogonadal. That context is missing entirely.

• Real symptoms of low testosterone include reduced libido, fatigue, loss of muscle mass, mood changes, and reduced ejaculatory volume, not just NPT changes.
• Absent morning erections can also indicate cardiovascular risk, which is arguably more urgent than a testosterone question.

What should you actually know?

Morning erections are a useful informal signal, but they are not a testosterone test. If you're regularly not experiencing them, yes, talk to a doctor. But the conversation should include a full picture: sleep quality, medications you're taking, blood pressure and metabolic health, stress levels, and then, among other blood tests, total and free testosterone.

Hypogonadism is diagnosed by blood test, specifically by two morning serum testosterone measurements below the lab reference range (typically under 300 ng/dL), combined with clinical symptoms. The Endocrine Society's 2018 clinical practice guidelines, published in Journal of Clinical Endocrinology and Metabolism, are explicit that no single symptom should trigger a testosterone diagnosis without lab confirmation.

The other thing worth knowing: treating absent morning erections as purely a testosterone problem can delay diagnosis of cardiovascular disease or diabetes, both of which cause erectile and NPT dysfunction through vascular and neurological damage. Rosen et al. (2004) in European Urology found that ED often precedes a cardiac event by several years, making it a potential early warning sign that deserves real medical evaluation, not just a testosterone supplement recommendation.