@seanstax2's testosterone and facial hair claims checked

What did @seanstax2 actually say?

The claim is straightforward: "If you can't grow a mustache by the age of 16, then you probably have low testosterone." He also says "reduced body hair and facial hair is actually an early sign of low testosterone" and recommends using a branded AI tool to check your levels. The video is tagged with a sponsor, so this is promotional content dressed up as health advice.

To be fair, he does say to "get it checked out" rather than self-treat, which is the one piece of reasonable advice buried in here. But the framing is still misleading because it turns a normal variation in adolescent development into a symptom requiring investigation.

Does the science back this up?

Partially, but only in the wrong direction. The claim conflates two very different things: normal variation in puberty timing and clinical hypogonadism in adult men. The science does not support using facial hair at 16 as a diagnostic marker for low testosterone.

Puberty timing varies enormously. The American Academy of Pediatrics notes that puberty in boys can begin anywhere between ages 9 and 14, and facial hair, specifically upper lip hair, typically appears 2 to 3 years after pubic hair development begins. That means a 16-year-old with minimal mustache growth may simply be a late bloomer, not hypogonadal. Groth et al. (2013, Pediatrics) documented this wide variation extensively. Genetic factors, particularly ethnicity, also play a large role. Men of East Asian or Native American descent often have significantly less facial hair regardless of testosterone levels, as noted by Randall (2008, Journal of Investigative Dermatology Symposium Proceedings).

Where the creator has a sliver of a point: in adult men who previously had normal facial hair and then experience loss, that can sometimes reflect declining androgens. But that is a completely different scenario from a teenager who has not yet grown a mustache.

What did they get wrong (or right)?

He got the adult symptom partially right but applied it to the completely wrong population. Reduced facial hair is listed among signs of hypogonadism in adult men by the Endocrine Society (Bhasin et al., 2010, Journal of Clinical Endocrinology and Metabolism), but in that context it means hair loss in someone who had hair, not delayed onset in a still-developing teenager.

What he got wrong:

• Age 16 is not a cutoff for mustache development. Facial hair development in adolescent males routinely extends into the late teens and early twenties.
• Ethnicity is a major confounder he completely ignores. Genetic variation in androgen receptor sensitivity and 5-alpha reductase activity can produce minimal facial hair in men with completely normal testosterone levels (Randall, 2008).
• He implies his own AI tool result proves the methodology, which is not evidence of anything clinically useful.
• The phrase "I'm actually on the higher end" while showing an app result is not a substitute for a serum total or free testosterone test ordered by a clinician.

One thing he did correctly: he suggested getting checked out rather than immediately supplementing. That is better than most TRT influencer content.

What should you actually know?

If you are a teenager worried about facial hair, the far more likely explanation is normal variation, not a hormonal disorder. Genuine hypogonadism in adolescents is uncommon and comes with a broader clinical picture including delayed puberty overall, not just one feature like a mustache.

If you are an adult male who has noticed changes in body hair alongside other symptoms like fatigue, low libido, or mood changes, that is a more reasonable reason to get a serum testosterone test. The Endocrine Society recommends testing total testosterone in the morning on at least two occasions before any diagnosis is made. A consumer AI app is not a diagnostic tool, and no reputable clinician would treat based on one.

The bottom line: facial hair pattern at 16 is a poor proxy for testosterone status. If you or a parent are genuinely concerned about delayed puberty, a pediatric endocrinologist can assess bone age, LH, FSH, and testosterone together, not a single feature in isolation. Do not let a sponsored TikTok video send you chasing a hormonal diagnosis you almost certainly do not have.