A sixteen-year-old arrives with a report. Ultrasound: “polycystic ovaries”. A diagnosis has already been made elsewhere, a prescription has already been written, and she has already been told she may struggle to have children one day.
Frequently, none of that was warranted.
The problem with diagnosing PCOS in adolescence
Polycystic ovary syndrome in adults is defined by a combination of irregular ovulation, clinical or biochemical excess of androgens, and polycystic ovarian morphology on ultrasound. Two of the three, with other causes excluded.
Applied to a teenager, two of those three criteria fall apart.
Irregular cycles are normal early on. In the first one to two years after menarche, anovulatory and irregular cycles are the physiological norm, because the axis is still maturing. Cycles between roughly 21 and 45 days are considered acceptable in this window.
Multifollicular ovaries are normal too. The adolescent ovary frequently looks “polycystic” on ultrasound simply because that is what a healthy pubertal ovary looks like. This is why pelvic ultrasound is not recommended as a diagnostic criterion in adolescents at all, and ordering one to make the diagnosis is the commonest error in this area.
Which leaves androgen excess doing most of the work, and that has to be assessed properly, not assumed from acne alone.
What the diagnosis should rest on in a teenager
Current international guidance is deliberately conservative:
- Persistent menstrual irregularity judged against how long it has been since menarche, not against an adult standard
- Plus clinical or biochemical hyperandrogenism: significant hirsutism, or a genuinely raised testosterone measured with a reliable assay
- Not ultrasound
- And other causes excluded
Where the picture is uncertain, the correct answer is often “at risk of PCOS” with a plan to reassess after some years, rather than a diagnosis. That framing is not fence-sitting. It gives the young woman a monitoring plan without giving her a label she may not need to carry.
What must be ruled out first
Several conditions look like PCOS and are managed entirely differently:
- Thyroid disease. Hypothyroidism disrupts cycles
- Hyperprolactinaemia
- Non-classical congenital adrenal hyperplasia. Checked with an early-morning 17-hydroxyprogesterone
- Pregnancy, which should be considered without embarrassment
- Hypothalamic amenorrhoea. From low energy availability, intense sport or an eating disorder. This is important and frequently missed, because it can superficially resemble PCOS and is treated in almost the opposite way
- Androgen-secreting tumours. Rare, but suggested by rapid virilisation
Why over-diagnosis is not harmless
A label given at sixteen tends to stay. It shapes how a young woman thinks about her body, her fertility and her future, often for decades, and it is rarely revisited. It can also close down the search for what is actually going on, with a hypothalamic cause missed because everyone stopped looking once “PCOS” was written down.
And it drives treatment that may be unnecessary. Which brings up the other common error.
What treatment actually looks like
There is no cure, but PCOS is very manageable, and treatment should be aimed at the symptom that is troubling the young woman, not at the ultrasound.
- Irregular periods. A combined oral contraceptive pill regulates cycles and protects the uterine lining. Cyclical progestogen is an alternative.
- Hirsutism and acne. The pill helps; dermatological measures and, if needed, anti-androgens have a role. Expect six months before judging any of it.
- Insulin resistance. Metformin has a place in specific situations, particularly with impaired glucose tolerance or significant metabolic features. It is not a routine first step for everyone.
- Weight, where relevant. Even modest changes in physical activity and diet improve cycles measurably. But this must be handled with real care in adolescents. Weight-focused conversations in this age group can precipitate disordered eating, and PCOS already carries a raised risk of it.
Not every girl with PCOS is overweight, and telling a lean adolescent to lose weight because of a diagnosis is both useless and harmful.
What I would want a teenager to hear
That irregular periods in the first couple of years are usually just her body learning the routine. That the ultrasound she may have already had probably should not have been done. That if she does have PCOS, the great majority of women with it who want children go on to have them. And that the acne, the hair and the cycles are all treatable, separately and on her own timetable, starting with whichever one is bothering her most.
General information for families. Diagnosis and treatment of PCOS in an adolescent should be individualised by a paediatric endocrinologist or adolescent gynaecologist.