Delayed Puberty
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Direct answer
Delayed puberty in a girl is absence of breast budding (thelarche) by age 13 years or absence of menarche by age 15 (or within three years of thelarche), and its workup hinges on a single branching test — serum FSH. High FSH means the ovary is failing (hypergonadotropic hypogonadism), with Turner syndrome (45,X and variants) the classical cause, demanding a karyotype; low or normal FSH points to a central cause or simply late but normal physiology. Treatment treats the cause and, where hypogonadism is permanent, induces puberty with gradually escalating oestrogen and later adds progestogen — Turner syndrome additionally needs growth hormone early and removal of any Y-chromosomal gonadal tissue.
What you must remember
- Thresholds to quote — no thelarche by 13 years, or no menarche by 15 years or within three years of the start of breast development, defines delay (roughly 2-2.5 standard deviations beyond the mean age of 10 for thelarche and 12-13 for menarche).
- The branching test — FSH after history and examination: elevated suggests primary ovarian failure; low or inappropriately normal suggests hypothalamic-pituitary causes; then prolactin, TSH and bone age complete the picture.
- Constitutional delay — the commonest overall explanation, with a family history of late puberty, delayed bone age matching height age, and eventual complete maturation; a diagnosis of exclusion, more frequent in boys.
- Hypergonadotropic causes — Turner syndrome (45,X or mosaic), and other primary ovarian insufficiency (autoimmune, post-chemotherapy or radiotherapy, galactosaemia).
- Hypogonadotropic causes — chronic systemic illness, anorexia nervosa and excessive exercise, hypothyroidism, hyperprolactinaemia, congenital GnRH deficiency (including Kallmann syndrome with anosmia), and pituitary tumours.
- Turner syndrome essentials — short stature, webbed neck, low posterior hairline, wide-spaced nipples, cubitus valgus, coarctation of the aorta, streak gonads; karyotype is confirmatory; any Y-chromosomal material mandates gonadectomy because of gonadoblastoma risk.
- Turner management sequence — growth hormone in childhood to maximise height, oestrogen initiated around 11-12 years at low dose and slowly escalated over two to three years, progestogen added once bleeding occurs to protect the endometrium, and fertility only with donor oocyte IVF in dedicated programmes.
- Puberty induction principles — start low, go slow to avoid premature epiphyseal fusion, and add cyclical progestogen once bleeding appears.
- Pelvic ultrasound and bone-age X-ray support the assessment; pituitary MRI is reserved for low FSH with headache, visual defects or very low gonadotrophins.
Working through a 15-year-old with no periods
A 15-year-old is brought by her mother: no breast development to speak of, no periods, and she is the shortest in her class at 141 cm. History — chronic illness, weight loss, sporting intensity, sense of smell, family pattern of late menarche. Examination — height below the third centile, Tanner B2 or less, a short webbed neck, low hairline, wide carrying angle, and a precordial bruit suggesting coarctation.
Her FSH comes back markedly elevated — the problem is her ovaries, not her brain — so a karyotype is sent, returning 45,X. Turner syndrome is confirmed, and echocardiography, renal ultrasound and audiology complete the systemic screen every new Turner diagnosis deserves. She is 15, so the pubertal window is nearly spent: oestrogen begins now — had she presented at 10, growth hormone would have come first, because oestrogen closes growth plates and the height battle is lost if it wins early.
Her regimen mimics physiology: low-dose transdermal oestradiol increasing over 12-24 months until breast development progresses and withdrawal bleeding appears, at which point cyclical progestogen is added — unopposed oestrogen invites endometrial hyperplasia. Lifelong hormone replacement and cardiac surveillance follow, since aortic dissection risk persists; fertility counselling is honest — ovum donation IVF is the realistic route, and pregnancy requires a cardiac go-ahead. Contrast her with a tall, thin ballerina of 15 with low FSH, delayed bone age and a mother whose menarche came at 15 — constitutional delay, managed with reassurance, weight optimisation and review.
High-yield viva angles
Examiners probe the single-test logic: FSH first, karyotype if high, MRI if suspiciously low. They probe the timing paradox in Turner — growth hormone early, oestrogen late and slow, because each helps one goal and harms the other. The Y-chromosome rule (gonadectomy for gonadoblastoma risk) is a standalone mark earner, as is the Kallmann pairing of anosmia with absent GnRH.
Frequently asked questions
At what ages is puberty considered delayed in a girl?
No breast budding by 13 years, or no menarche by 15 years or within three years of thelarche — roughly 2-2.5 standard deviations beyond population means.
Why is FSH the key branching investigation?
It separates ovarian failure (high FSH, needing karyotype) from central or constitutional causes (low or normal FSH, needing further central evaluation).
How is puberty induced in Turner syndrome?
With gradually escalating low-dose oestrogen over two to three years, adding cyclical progestogen once bleeding begins; growth hormone is given earlier in childhood to secure final height.
Why is gonadectomy advised in Turner syndrome with Y material?
Streak gonads carrying Y-chromosomal material carry a substantial risk of gonadoblastoma, so they are removed once the karyotype is known.