Premature Puberty Puberty And Related Disorders
Premature puberty is the onset of secondary sexual characteristics before age 8 in girls or age 9 in boys, resulting from early activation of the hypothalamic-pituitary-gonadal axis (central) or peripheral sex steroid production (peripheral).
Premature Puberty: Puberty and Related Disorders
Lecture Map
This lecture is fundamentally about understanding the hormonal axis that drives puberty (the HPG axis), recognizing when puberty occurs too early, distinguishing benign variants from pathological causes, and knowing when and how to treat. The core clinical skill is: a child presents with early secondary sexual characteristics — is this dangerous, does it need treatment, and what workup do I order?
- Normal pubertal development
- Definition of precocious puberty
- Variations of normal pubertal development
- Causes of precocious puberty
- Management of precocious puberty
- Paediatric endocrinology is a classic short-answer / mini-case topic. Expect a vignette of a young girl with breast development or a boy with enlarged testes — you need to classify central vs. peripheral, list investigations, and outline management.
- Turner syndrome, congenital adrenal hyperplasia (CAH), and McCune-Albright syndrome overlap with genetics, surgery, and O&G teaching and are favourite exam discriminators.
- Past papers have tested Turner syndrome features directly [3].
1. Normal Pubertal Development — First Principles
Kisspeptins from the hypothalamus bind to a G protein-coupled receptor called GPR54 on hypothalamic neurons to secrete GnRH. [1]
Why kisspeptin matters: Before puberty, the GnRH pulse generator is dormant. The "switch" that turns it on is kisspeptin signalling. Think of kisspeptin as the ignition key for puberty. Loss-of-function mutations in kisspeptin or GPR54 → no puberty (hypogonadotropic hypogonadism). Gain-of-function mutations → precocious puberty.
Puberty onset is a central process with activation of the GnRH pulse generator. [1]
The sequence is:
- Hypothalamus → episodic/pulsatile GnRH release
- Anterior pituitary → pulsatile LH and FSH secretion
- Gonads → oestrogen (ovaries) or testosterone (testes)
Gonadotropin release is controlled by GnRH and selective negative feedback inhibition of gonadal steroids at pituitary and hypothalamic levels. [1]
Why pulsatility matters clinically: Continuous (non-pulsatile) GnRH → downregulation of GnRH receptors on the pituitary → suppression of LH/FSH. This is exactly the mechanism exploited by GnRH analogues (e.g., leuprolide) used to treat central precocious puberty — constant GnRH exposure paradoxically shuts off the axis.
Onset of puberty is also modulated by: genetic factors; peripheral signs (intrauterine and postnatal growth, BMI and fat mass, insulin sensitivity, gonadal steroid levels); environmental signals (light, stress, environmental endocrine disruptors). [1]
| Modulator | Mechanism / Example |
|---|---|
| Genetic factors | Family history of early/late puberty; mutations in kisspeptin/GPR54 |
| Nutritional status / BMI | Higher BMI → more leptin → permissive for GnRH pulsatility. Explains why obesity is associated with earlier puberty and anorexia with delayed puberty |
| Insulin sensitivity | Insulin resistance (as in SGA children) → earlier adrenarche |
| Intrauterine growth | SGA → catch-up growth → earlier puberty onset [1] |
| Environmental endocrine disruptors | Xenoestrogens (pesticides, plasticizers) mimic oestrogen → stimulate target tissues |
| Light | Melatonin inhibits GnRH; prolonged light exposure may lower melatonin |
| Stress | Chronic stress can suppress or advance pubertal timing depending on context |
Puberty starts in both sexes around 11 years of age. More evident in girls because of breast development and the onset of growth spurt. [1]
Breast development is caused by oestrogen and may be unilateral for several months. [1]
High Yield – Unilateral Breast Development
Do not mistake unilateral breast budding for a pathological breast mass. It is common for breast development to start on one side before the other and can remain asymmetric for months. This is a normal variant, not a reason for biopsy.
Pubic and axillary hair growth is under the influence of adrenal androgens but the stage of breast development usually correlates well with the stage of pubic hair development. [1]
Key point: Breast development = oestrogen effect. Pubic/axillary hair = adrenal androgen effect (adrenarche). These are two separate hormonal processes that usually track together but can dissociate (e.g., isolated premature thelarche vs. isolated premature adrenarche).
Growth and Menarche Milestones in Girls
| Milestone | Timing | Key Detail |
|---|---|---|
| Breast buds (B2) | Mean 10.1 years | First sign of puberty in girls |
| Sparse pubic hair (P2) | Mean 11.2 years | Adrenal androgen-driven |
| Growth spurt | Mean 12.2 years | Peak height velocity (PHV) is attained 6-9 months after B2 |
| Menarche | Mean 12.7 years | Occurs 2-2.5 years after breast budding |
| Adult pubic hair (P5) | Mean 14 years | |
| Mature breast (B5) | Mean 14 years |
The first menstrual bleedings are anovulatory. Time from menarche to regular cycling is about 3 years. [1]
This is why irregular periods in the first few years after menarche are physiological — the HPG axis has not yet matured enough for consistent ovulatory cycles. Don't rush to diagnose PCOS in a 13-year-old with irregular periods.
The average girl will grow for another 6-7 cm after menarche. [1]
Exam Trap
A common mistake: assuming growth stops at menarche. In reality, there is still ~6-7 cm of residual growth after menarche, but growth velocity has already slowed significantly. This is clinically important when predicting adult height in a girl with precocious puberty.
First sign of puberty is increase in testicular volume to 4 mL, due to enlargement of Sertoli cells rather than Leydig cells. [1]
Why Sertoli cells first? FSH stimulates Sertoli cell proliferation (they support spermatogenesis). Leydig cells (testosterone production, stimulated by LH) enlarge later. This is why the earliest testicular enlargement is not accompanied by virilization — it's FSH-driven, not LH/testosterone-driven.
Growth of penis and genitalia correlate well with pubic hair development as both are regulated by androgen. [1]
Boys have peak growth spurt during mid-puberty, at mean 13.5 years, corresponding to testicular volume of 10-12 mL. [1]
Critical sex difference: Girls have their growth spurt EARLY in puberty (around B2-B3), while boys have theirs in MID-puberty. This is why boys end up taller on average — they have 2 more years of prepubertal growth before their spurt begins.
Spermatogenesis histologically from 11-15 years. Sperm found in early morning urine at mean of 13.3 years. Ejaculation occurs by a mean of 13.5 years. [1]
Adult morphology, motility and concentration of sperm are not found until bone age advances to 17 years but immature-appearing boys can be fertile. [1]
Clinical Pearl
An immature-appearing boy can still be fertile. This has medicolegal relevance when counselling adolescents. Don't assume infertility based on appearance alone.
Gynaecomastia in Boys
Breast enlargement is common during early puberty because of oestrogen production by aromatization of testosterone before testosterone achieves concentrations that can oppose the oestrogen. Breast tissue often regresses within 2 years. [1]
Occasionally gynaecomastia remains permanent in normal, often obese, boys and frequently in pathological conditions such as Klinefelter syndrome or partial androgen resistance, in which the effective amount of bioactive testosterone is reduced. [1]
Why this matters: Pubertal gynaecomastia is usually self-limiting (2 years). Persistent gynaecomastia should prompt investigation for Klinefelter syndrome (47,XXY), liver disease, or drug causes.
Used for determination of testicular volume. [1] This is a string of graded ellipsoid beads (1-25 mL). Clinically:
- Prepubertal: < 4 mL
- Pubertal onset: ≥ 4 mL
- Mid-puberty / peak growth: 10-12 mL
- Adult: 15-25 mL
Onset of puberty at a younger age than expected for the normal population (i.e. > 2 SDs earlier than population mean). [1]
Classically, pubertal signs occurring before 8 years for girls or 9 years for boys have been considered precocious. [1]
High Yield – Age Cutoffs
Girls: < 8 years. Boys: < 9 years. These are the classic cutoffs you must know for exams. The 1-year difference reflects that boys normally enter puberty ~1 year later than girls.
2.1 The Controversy — Should the Cutoff Be Lowered?
Data from the PROS network (>17,000 girls) suggested puberty may be occurring earlier than previously thought: White girls with thelarche at a mean of 9.96 ± 1.82 years; Black girls with thelarche at a mean of 8.87 ± 1.93 years. [1]
LWPES (now Pediatric Endocrine Society) recommended lowering age cutoff for precocious puberty to < 7 years in white girls and < 6 years in black girls. [1]
Pubertal onset occurring between 7-8 years in white girls and 6-8 years in black girls should be evaluated if there is: unusually rapid pubertal progression resulting in bone age advancement by > 2 years and a predicted height < 150 cm or 2 SDs below genetic target height; signs and symptoms of a CNS lesion; behaviour-based factors suggesting adverse emotional effects from early puberty. [1]
New guidelines not universally accepted by endocrinologists and several have questioned the validity of the PROS study. [1]
Exam framing (GC lecture): For HKUMed exams, use the classic cutoffs (< 8 years girls, < 9 years boys) unless the question specifically references different racial cutoffs. The lecture emphasizes these new data are "not universally accepted."
Sexual development in girls younger than 8 years and boys younger than 9 years need a thorough history and examination, a bone age and close longitudinal follow up. [1]
Not all organic aetiologies and certainly not the normal variants require treatment. [1]
4. Variations of Normal Pubertal Development (50-60% of presentations)
50-60% only one secondary sexual characteristic shows premature development: isolated premature thelarche, isolated premature adrenarche, isolated premature menarche. Aetiology should be sought and need monitoring to prevent precocious onset of puberty. [1]
Isolated breast development in girls between 2-7 years. [1]
This differs from the genital crisis of the newborn whose breast development (associated with strong oestrogenization and even milk production) may last for the first 18 months of life. [1]
Why the neonatal distinction matters: Neonatal breast tissue is caused by maternal/placental oestrogen withdrawal. It's physiological and resolves by 18 months. Premature thelarche occurring after this period (2-7 years) is the entity we're discussing.
Bilateral in half the cases, unilateral, or less frequently asymmetric. Volume varies: 60% at B2, 30% at B3, 10% at B4. [1]
Breast often tender and palpation sometimes painful. No discharge. [1]
If persistent or marked thelarche → LHRH test. LHRH test shows predominant FSH response. [1]
Why FSH-predominant? In premature thelarche, there is a slight increase in FSH (which stimulates small amounts of ovarian oestrogen), but LH remains suppressed. This is fundamentally different from central precocious puberty, where LH is elevated (pubertal pattern). The FSH-predominant response on GnRH stimulation test is the key discriminator.
Bone maturation rarely accelerated. [1]
Progression characterized by fluctuation over time: spontaneous remission, persistence, and aggravation of breast volume, which should evoke the possibility of pubertal onset. [1]
30-60% regress within an average of 18 months. [1]
In the usual form, premature thelarche does not require any treatment. [1]
High Yield – Premature Thelarche vs. CPP
| Feature | Premature Thelarche | Central Precocious Puberty |
|---|---|---|
| Age | 2-7 years | Any < 8y |
| Isolated finding | Yes (breast only) | No (multiple signs + growth acceleration) |
| Growth velocity | Normal | Accelerated |
| Bone age | Normal or mildly advanced | Significantly advanced |
| GnRH stimulation test | FSH-predominant | LH-predominant (pubertal pattern) |
| Progression | Fluctuates, often regresses | Progressive |
| Treatment | None (monitor) | GnRH analogue if indicated |
4.2 Premature Adrenarche / Pubarche
The appearance of pubic hair before 8 years. More commonly in girls than in boys. Usually isolated but occasionally axillary hair observed. [1]
Clinical exam to detect other signs of hyperandrogenism: acne, abnormal perspiration, clitoral hypertrophy. [1]
Growth velocity and bone age maturation are usually only slightly accelerated. [1]
Workup:
An androgen work-up (testosterone, 17OHP, DHEAS) +/- a synacthen test to exclude congenital adrenal hyperplasia. [1]
Why 17OHP? 17-hydroxyprogesterone (17OHP) is the substrate that accumulates proximal to the 21-hydroxylase enzyme block in CAH. Elevated 17OHP (especially after ACTH stimulation / Synacthen test) is diagnostic of 21-hydroxylase deficiency, the commonest cause of CAH (>90%) [4].
In most situations, the maturation of the adrenal function that precedes puberty is accelerated or early (premature adrenarche), although the reason remains unknown. [1]
Exaggerated adrenarche is an extreme type of premature adrenarche — girls with subtle androgen excess (e.g., significant bone age advancement but not clitoromegaly) or insulin resistance (e.g., central adiposity or acanthosis nigricans). Often with slightly advanced onset of true puberty, but height potential not compromised. Adrenal steroid levels in mid- or late pubertal range. Testosterone not exceeding lower end of adult female range. [1]
Still unclear whether a normal variant due to advanced onset of normal zona reticularis development or an early manifestation of the steroidogenic dysregulation of polycystic ovary syndrome (PCOS) with cardiometabolic risk factors. [1]
Premature pubarche carries a 15-20% risk of developing PCOS, especially in those with exaggerated adrenarche. [1]
Girls with premature adrenarche should be followed through puberty. [1]
Clinical Pearl
Premature adrenarche is usually benign, but these girls need long-term follow-up because of the 15-20% risk of developing PCOS later. Look for signs of insulin resistance (acanthosis nigricans, central adiposity) as predictors.
Poorly defined and understood. Menstruation without other signs of puberty in a young girl before 9 years of age. [1]
Must exclude foreign body, local masses, and McCune-Albright syndrome. [1]
Transient ovarian activity has been observed in isolated premature menarche. [1]
Several clinical manifestations: menstruation that is isolated or associated with breast development, with inconsistent response to LHRH test and the frequent presence of functional ovarian cysts. [1]
These rises in oestrogenisation increase the risk of accelerated bone maturation. [1]
Treatment to stop puberty is often discussed but rarely undertaken. [1]
Important DDx for Vaginal Bleeding in a Young Girl
Before diagnosing "isolated premature menarche," you MUST rule out:
- Vaginal foreign body (most common cause of vaginal bleeding in prepubertal girls)
- Vulvovaginitis / trauma / sexual abuse
- Local tumours (sarcoma botryoides / rhabdomyosarcoma of vagina)
- McCune-Albright syndrome (autonomous ovarian cysts)
- Exogenous oestrogen exposure
Primary hypothyroidism: TSH is a weak agonist at FSH receptor resulting in ovarian stimulation with isolated breast development in girls. In boys, testicular enlargement without other secondary sexual characteristics may occur. [1]
Why does this happen? TSH and FSH share a common α-subunit. When TSH is massively elevated (as in severe primary hypothyroidism), the excess TSH cross-reacts with the FSH receptor (and to a lesser extent the LH receptor). This is called "overlap" or "specificity spillover." The result is gonadal stimulation without true HPG axis activation.
No pubertal progression in majority of cases. Delayed bone age with poor growth velocity. [1]
This is a key discriminator: In true precocious puberty, bone age is advanced. In hypothyroidism-related precocious puberty, bone age is delayed and growth velocity is poor. This is the opposite of what you'd expect with other causes, making it a favourite exam trap.
Excellent prognosis with reversal of puberty once treatment is started but final height may be affected if diagnosis is delayed or if normal puberty progresses at an early age. [1]
5. Pathological Causes of Precocious Puberty
Isosexual pubertal development with pubertal changes appropriate for the sex of the child: breast budding in girls, testicular enlargement in boys. [1]
Results from activation of HPG axis at an earlier age. [1]
At least 80% idiopathic in girls vs 10% idiopathic in boys. [1]
High Yield – Sex Difference in CPP Aetiology
Girls: 80% idiopathic → most cases are benign
Boys: Only 10% idiopathic → must exclude CNS tumour in all boys with CPP
This is one of the most important clinical pearls in paediatric endocrinology. A boy with precocious puberty gets an MRI brain. Period.
Most concerning causes are tumours arising in the suprasellar region, with or without (usually anterior) pituitary hormonal deficiencies. [1]
Most common cause of CPP in the very young child is benign hypothalamic hamartoma. [1]
Why hamartoma causes CPP: Hypothalamic hamartomas contain ectopic GnRH-secreting neurons that fire autonomously, activating the HPG axis prematurely. They are benign (not malignant) and may also cause gelastic seizures (laughing seizures). They are sometimes managed conservatively (GnRH analogue for puberty, anti-epileptics for seizures) rather than surgically.
Other CNS causes of CPP:
- CNS tumours (glioma, astrocytoma, pinealoma, craniopharyngioma)
- Post-CNS infection (meningitis, encephalitis)
- Post-CNS irradiation
- Hydrocephalus
- Head trauma
- Neurofibromatosis type 1 (optic glioma can involve hypothalamus → CPP) [5]
Progresses rapidly and the accelerated bone maturation causes early fusion of bone plates and compromising final adult height. [1]
Gonadal or adrenal sex steroid secretion not resulting from activation of HPG axis, i.e. pituitary independent or peripheral in origin. [1]
Loss of normal feedback and sex steroid concentrations can be very high with low gonadotropins. [1]
Can involve isolated androgen, isolated oestrogen, or combined androgen and oestrogen production. [1]
Key biochemical pattern: High sex steroids + LOW (suppressed) LH and FSH. This is the opposite of CPP where LH/FSH are elevated/pubertal.
Can be isosexual OR contrasexual [2]:
- Isosexual: Feminization in girls (oestrogen-producing ovarian cyst) or virilization in boys (testosterone-producing tumour)
- Contrasexual: Virilization in girls (adrenal tumour, CAH) or feminization in boys (oestrogen-secreting tumour, aromatase excess)
| Cause | Mechanism | Key Features |
|---|---|---|
| Ovarian cyst/tumour | Autonomous oestrogen production | Breast development, vaginal bleeding in girls |
| Adrenal tumour | Autonomous androgen/oestrogen | Virilization, Cushing features if cortisol co-secretion |
| CAH (non-classical) | 21-hydroxylase deficiency → androgen excess | Pubic hair, acne, accelerated growth, elevated 17OHP |
| hCG-secreting tumour | hCG acts on LH receptor → testosterone in boys | Hepatoblastoma, mediastinal germ cell tumour |
| Exogenous sex steroids | Environmental or accidental exposure | History of exposure, creams, xenoestrogens |
| McCune-Albright syndrome | Constitutive Gsα activation | See below |
| Familial testotoxicosis (FMPP) | Constitutive LH receptor activation | Boys only, see below |
It has become increasingly evident that the hyperoestrogenism may have an exogenous cause, such as environmental chemical pollutants in the air, water, and food chain. These xenoestrogens have a chemical structure that mimics the actions of natural oestrogens by stimulating the activity of target tissues. [1]
5.3 McCune-Albright Syndrome (MAS)
Multisystem disorder of both boys and girls but much more commonly in girls. [1]
Characterised by triad of: (1) Irregularly edged hyperpigmented macules or café au lait spots "coast of Maine"; (2) Polyostotic fibrous dysplasia; (3) Multiple autonomous endocrinopathies — most commonly gonadotropin-independent sexual precocity; other endocrine involvement includes the thyroid, the adrenals, the pituitary and the parathyroids. [1]
At least 2 of these features should be present for the diagnosis to be made. [1]
High Yield – McCune-Albright vs. NF1 Café-au-Lait Spots
| Feature | McCune-Albright | NF1 |
|---|---|---|
| Borders | Jagged "coast of Maine" | Smooth "coast of California" |
| Distribution | Respect the midline (ipsilateral) | Bilateral, any location |
| Number | Usually fewer, larger | ≥ 6 diagnostic |
| Associated conditions | Fibrous dysplasia, precocious puberty | Neurofibromas, optic glioma |
Sporadic condition due to a somatic activating missense mutation in the gene encoding the α-subunit of the G-protein that stimulates cAMP production (Gsα). [1]
The mutation occurs early in embryogenesis (somatic or postzygotic, rather than germ cell in origin) and results in failure of phosphorylation of GTP to GDP and thereby constitutive activation of adenylyl cyclase in multiple affected tissues. [1]
From first principles: Normally, G-protein signalling is self-limiting because the Gsα subunit has intrinsic GTPase activity (it hydrolyzes GTP → GDP, turning itself off). The MAS mutation abolishes this GTPase activity → Gsα is stuck in the "on" position → continuous cAMP production → continuous hormonal activation in affected tissues.
Because it's a somatic mosaic mutation (occurs post-zygotically), only some cells carry the mutation → the pattern of affected tissues is unpredictable and asymmetric (hence why café-au-lait spots respect the midline — the mutant clone stays on one side of the embryonic developmental boundary).
Such mutations may also occur in the skin, bones, liver (cholestasis), heart (arrhythmias) and GI tract. [1]
Sexual precocity in girls is caused by autonomously functioning luteinized follicular cysts of the ovaries. Multiple follicular cysts with an occasional large solitary cyst may be present. [1]
Oestrogen production is associated with a prepubertal pattern of LH secretion with absent LH response to GnRH. [1]
This is the hallmark of peripheral (GnRH-independent) precocious puberty: high oestrogen, suppressed LH/FSH, no response to GnRH stimulation.
Later GnRH-dependent puberty ensues with ovulatory cycles. [1]
Important: over time, the chronic oestrogen exposure can secondarily activate the HPG axis (a phenomenon where peripheral precocious puberty "triggers" central precocious puberty).
Sexual precocity is rare in boys with MAS; when it occurs, it is associated with asymmetric enlargement of the testes in addition to signs of sexual precocity. [1]
Rare familial condition. Gonadotropin-independent precocious puberty only in boys, often presenting at 2-5 years with accelerated growth, early secondary sexual characteristics and reduced adult height. Testes show only little increase in size. Biopsy shows Leydig cell hyperplasia. [1]
Autosomal dominant inheritance only in males. Associated with a number of constitutively activating mutations of LH receptor, mostly in the transmembrane domain of the receptor. [1]
Mechanism: Activating mutation in LH receptor → receptor is "on" even without LH binding → autonomous testosterone production by Leydig cells. This is analogous to MAS (constitutive Gsα activation) but the mutation is specifically in the LH receptor gene.
Virilization with very high concentrations of testosterone and enlargement of testes to the early to mid-pubertal range, although seem smaller than expected in relation to stage of penile growth. [1]
Why small testes relative to virilization? Because the testes are NOT being stimulated by FSH (the seminiferous tubules, which make up most of testicular volume, are not growing). Only the Leydig cells are hyperactive → testosterone is high but testicular volume is disproportionately small for the degree of virilization.
Unstimulated gonadotropin concentrations are prepubertal with a minimal response to GnRH stimulation. Lack of the usual pubertal pattern of LH pulsatility. [1]
Fertility and a normal pattern of LH secretion and response to GnRH are demonstrated in adulthood. [1]
Treatment with androgen-receptor-blocking agents (ketoconazole) or aromatase inhibitors. [1]
Why GnRH analogues DON'T work: FMPP is GnRH-independent. The testes are producing testosterone autonomously. Shutting down pituitary LH (which is already low) won't help. Instead, you need to block the downstream effects:
- Ketoconazole: Inhibits steroidogenic enzymes (blocks testosterone synthesis)
- Spironolactone: Androgen receptor antagonist
- Aromatase inhibitors: Block conversion of testosterone to oestrogen (reduces oestrogen-mediated bone maturation)
6. Clinical Approach — Evaluation of Abnormal Puberty
1. Onset of puberty before 8 years? 2. Any progression of clinical symptoms? 3. Any biological or radiographic signs of exaggerated maturation? 4. Is the predicted adult height affected? 5. Any psychological consequences? 6. Gonadotropin-dependent or independent? 7. If CPP, is it due to a tumour or idiopathic? [1]
Birth history – SGA (more prone to precocious pubarche, earlier onset of pubertal development and menarche and faster progression of puberty than children born AGA). [1]
Past medical history: past x-rays, brain trauma, neonatal infection of the CNS. [1]
Family history (of early puberty, CAH, NF1, MAS)
Precise timing and sequence of pubertal milestones. [1]
Impact on psychological health or well-being. [1]
Additional history to consider:
- Exposure to exogenous hormones (creams, medications)
- Growth pattern (crossing centiles upward = concerning)
- Headaches, visual changes (CNS lesion)
- Seizures, especially gelastic seizures (hamartoma)
- Abdominal pain, swelling (ovarian/adrenal mass)
Focusing on the neurologic and endocrine systems. Thyroid examination. Stages of pubertal development – Tanner stages. Neurological exam, optic fundi, visual field. Neurocutaneous markers. Scoliosis or body asymmetry. Assessment of growth chart. [1]
| Examination Component | What You're Looking For |
|---|---|
| Tanner staging | Assess degree and type of pubertal development |
| Height/weight on growth chart | Crossing centiles? Accelerated linear growth? |
| Testicular volume (Prader orchidometer) | ≥ 4 mL = pubertal; bilateral vs. unilateral enlargement |
| Thyroid | Goitre → hypothyroidism as cause |
| Neurological exam | Papilloedema, visual field defects → CNS mass |
| Skin | Café-au-lait spots (MAS vs. NF1), acanthosis nigricans |
| Body asymmetry | Fibrous dysplasia (MAS) |
| Abdominal exam | Palpable mass (ovarian/adrenal tumour) |
Findings suggestive of pathology: a rapid tempo of progression, advanced development, rapid linear growth, advanced skeletal maturation. [1]
6.4 Investigations
Hormonal profile: LH, FSH, oestradiol/testosterone, TFT, prolactin and β-hCG. [1]
X-ray for bone age. [1]
LHRH test (GnRH stimulation test). [1]
Pelvic USG. [1]
MRI brain and pituitary gland. [1]
| Investigation | What It Tells You |
|---|---|
| LH, FSH | Central (elevated/pubertal) vs. peripheral (suppressed) |
| GnRH stimulation test (LHRH test) | Gold standard: LH-predominant response = CPP; FSH-predominant = premature thelarche; suppressed = peripheral cause |
| Oestradiol / Testosterone | Degree of sex steroid exposure |
| TFT (TSH, T4) | Primary hypothyroidism as cause |
| Prolactin | Elevated if pituitary stalk compression/prolactinoma |
| β-hCG | hCG-secreting tumour (hepatoblastoma, germ cell tumour) |
| Bone age X-ray (left wrist) | Advanced > 2 years = pathological; accelerated maturation → compromised adult height |
| Pelvic USG | Uterine size/shape (pubertal vs. prepubertal), ovarian cysts/masses |
| MRI brain | CNS tumour, hamartoma, other structural lesions |
USG pelvis and adrenals. Measurement of 17OHP, DHEAS and testosterone especially in girls with virilization to screen for non-classical congenital adrenal hyperplasia. Occasionally ACTH stimulation test. 24 hour urine free cortisol if suspicious of Cushing syndrome. [1]
If only one testis is enlarged, a radiological search for an androgen-producing tumour within the larger testis is mandatory. [1]
If both testes are enlarged, the aetiology is most often central, but FMPP must also be considered. [1]
| Testicular Finding in Boys | Most Likely Diagnosis |
|---|---|
| Both testes enlarged (≥ 4 mL) | Central precocious puberty (or FMPP) |
| One testis enlarged | Testicular tumour (Leydig cell tumour) |
| Both testes small despite virilization | Adrenal cause (CAH, adrenal tumour) — testes not stimulated |
| Asymmetric enlargement | McCune-Albright syndrome |
7. Management of Precocious Puberty
Not all cases of CPP require treatment. [1]
Reasons for treatment include: preservation of adult height potential; psychological difficulties with early puberty and menarche. [1]
Mainstay of treatment is GnRH analogues. Provides constant serum levels of GnRH activity and thus overrides the pulsatility of endogenous GnRH. [1]
Usual depot IM injection of leuprolide acetate once every 4 weekly. [1]
Mechanism revisited: Endogenous GnRH is pulsatile → stimulates LH/FSH. GnRH analogues given continuously (depot form) → initially a brief flare of LH/FSH (first 1-2 weeks), then downregulation of GnRH receptors → suppression of LH/FSH → regression of puberty.
Who Benefits Most?
Adult height preservation particularly in girls < 6 years with the greatest gain in adult height after treatment. [1]
Those between 6 and 8 years form a more heterogeneous group. Some with very rapid or advanced puberty may benefit. Many with slowly progressive puberty yield a normal height outcome without treatment. [1]
Little utility to treat girls over age 8 years for the purpose of increasing adult height. [1]
| Age at Presentation | Benefit of GnRH Analogue |
|---|---|
| < 6 years | Greatest height gain, strongly indicated |
| 6-8 years | Heterogeneous; treat if rapidly progressive |
| > 8 years | Little height benefit; consider only for psychosocial reasons |
Treatment depends on the cause: [1]
- Surgical removal of tumours ± chemotherapy and/or radiation therapy as indicated
- Large ovarian cysts: drainage under USG guidance
- Exogenous oestrogens or androgens: should be uncovered and eliminated
- Non-classical CAH: exogenous glucocorticoid
GnRHa therapy may be needed in addition to any of the above therapies if central puberty concomitantly starts at an early age. [1]
Why might you need GnRH analogue in peripheral precocious puberty? Chronic exposure to sex steroids from the peripheral cause can eventually "prime" the HPG axis and trigger secondary central precocious puberty. In this case, you treat both the peripheral cause AND add GnRH analogue for the central component.
8. Related Conditions Tested in Past Papers
From the 2025 Fourth Summative MCQ [3]:
A 15-year-old girl with height below the 0.4th centile, webbed neck, low-set ears, shield chest, cubitus valgus and Madelung deformities of the wrist. Blood pressure is 135/65 mmHg. Most likely diagnosis: Turner syndrome.
Why Turner syndrome is relevant here: Turner syndrome presents with delayed puberty (the opposite end of the spectrum), but understanding normal puberty helps you recognize when puberty fails to occur. Features:
- Short stature (SHOX haploinsufficiency)
- Gonadal dysgenesis → streak gonads → hypergonadotropic hypogonadism → absent puberty without oestrogen replacement
- Webbed neck, shield chest, cubitus valgus, coarctation of aorta (explains the wide pulse pressure BP of 135/65)
- Madelung deformity (wrist)
CAH (21-hydroxylase deficiency) can cause peripheral precocious puberty through androgen excess [4]:
- Classic (salt-wasting): Neonatal adrenal crisis, ambiguous genitalia in girls
- Classic (simple virilizing): Virilization in girls, precocious puberty in boys
- Non-classic (late onset): Premature pubarche, acne, accelerated bone age → easily confused with premature adrenarche
Screening: 17OHP levels; confirmatory with ACTH stimulation test.
9. Exam Intelligence
- Vignette: 6-year-old girl with bilateral breast development, no other pubertal signs, normal growth → premature thelarche
- Vignette: 5-year-old girl with breast development + pubic hair + accelerated growth + advanced bone age → central precocious puberty → order GnRH stimulation test + MRI brain
- Vignette: 3-year-old boy with enlarged penis, pubic hair, but SMALL testes → peripheral cause (adrenal tumour or CAH, not central)
- Vignette: Girl with café-au-lait spots with "coast of Maine" borders + vaginal bleeding + bone pain → McCune-Albright syndrome
- Vignette: Boy 4 years old with bilateral testicular enlargement + virilization, family history of early puberty → FMPP → treat with ketoconazole/aromatase inhibitor, NOT GnRH analogue
| Trap | Correct Answer |
|---|---|
| Assuming all precocious puberty needs treatment | Not all cases require treatment; slowly progressive CPP may not |
| Using GnRH analogue for peripheral precocious puberty | GnRH analogue only works for central causes; peripheral needs cause-specific treatment |
| Forgetting thyroid function tests | Primary hypothyroidism can mimic precocious puberty (but with delayed bone age!) |
| Not ordering MRI in boys with CPP | Boys have high rate of CNS pathology (90% non-idiopathic) |
| Confusing NF1 vs. MAS café-au-lait spots | NF1 = smooth "coast of California"; MAS = jagged "coast of Maine" |
| Bone age in hypothyroidism-related PP | DELAYED (unlike all other causes where it's advanced) |
Example question: "A 5-year-old girl presents with breast development (B3) and pubic hair (P2). She has grown 10 cm in the past year. What is your approach?"
Mark-scheme answer structure:
- This is precocious puberty (< 8 years in a girl) with progressive development and accelerated growth.
- History: timing, sequence, birth history (SGA?), family history, CNS symptoms, exposure to exogenous hormones, psychological impact.
- Examination: Tanner staging, growth chart, neurological exam, thyroid, neurocutaneous markers.
- Investigations: LH, FSH, oestradiol, TFT, β-hCG, prolactin; bone age X-ray; GnRH stimulation test; pelvic USG; MRI brain.
- If GnRH stimulation shows LH-predominant response → central precocious puberty → MRI brain to exclude tumour.
- Treatment: GnRH analogue (leuprolide depot q4 weekly) if progressive with compromised height potential or psychosocial distress. Greatest benefit if < 6 years.
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Define precocious puberty and give the classic age cutoffs. — Onset of puberty > 2 SD earlier than mean; < 8 years girls, < 9 years boys.
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What is the first sign of puberty in girls vs. boys? — Girls: breast budding (B2, mean 10.1y); Boys: testicular enlargement to ≥ 4 mL.
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How do you distinguish premature thelarche from CPP? — Premature thelarche: isolated breast development, no growth acceleration, normal bone age, FSH-predominant GnRH response, often regresses. CPP: multiple pubertal signs, accelerated growth, advanced bone age, LH-predominant GnRH response, progressive.
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Why is MRI brain mandatory in boys with CPP? — Only 10% of boys with CPP have idiopathic cause; 90% have an identifiable CNS lesion including tumours.
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Describe the triad of McCune-Albright syndrome. — (1) Café-au-lait spots with "coast of Maine" borders respecting midline; (2) Polyostotic fibrous dysplasia; (3) Autonomous endocrinopathies (most commonly GnRH-independent precocious puberty). Need ≥ 2 features for diagnosis.
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What is the molecular mechanism of McCune-Albright syndrome? — Somatic activating mutation in Gsα → loss of GTPase activity → constitutive activation of adenylyl cyclase → elevated cAMP → autonomous tissue activation.
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Why do GnRH analogues work in CPP but not in peripheral precocious puberty? — GnRH analogues suppress pituitary LH/FSH by overriding pulsatility with continuous stimulation → receptor downregulation. In peripheral PP, sex steroids are produced independently of LH/FSH, so suppressing gonadotropins has no effect.
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A child presents with precocious puberty and delayed bone age. What diagnosis should you consider? — Primary hypothyroidism (TSH cross-reacts with FSH receptor). Reversed by thyroid hormone replacement.
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What investigation screens for non-classical CAH in a girl with premature pubarche? — 17-hydroxyprogesterone (17OHP), DHEAS, testosterone; +/- ACTH stimulation (Synacthen) test.
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What is familial testotoxicosis (FMPP) and how is it treated? — Autosomal dominant activating mutation of LH receptor in males → GnRH-independent precocious puberty. Treated with ketoconazole (steroidogenesis inhibitor) or aromatase inhibitors (block oestrogen-mediated bone maturation). GnRH analogues are ineffective.
High Yield Summary
Precocious puberty = pubertal signs < 8y girls / < 9y boys.
- 50-60% are normal variants (isolated thelarche, adrenarche, menarche) → monitor, no treatment needed.
- 10-20% are central precocious puberty (HPG axis activation) → LH-predominant GnRH response, advanced bone age → MRI brain (especially in boys, where 90% have a CNS lesion) → treat with GnRH analogues (leuprolide q4 weekly) if height compromised or psychosocial distress; greatest benefit < 6 years.
- ~10% are peripheral precocious puberty (adrenal/gonadal/exogenous) → suppressed LH/FSH, high sex steroids → treat the cause (surgery, glucocorticoids for CAH, eliminate exogenous sources).
- McCune-Albright: café-au-lait "coast of Maine" + fibrous dysplasia + autonomous endocrinopathy; somatic Gsα mutation.
- Familial testotoxicosis (FMPP): boys only, activating LH receptor mutation, GnRH-independent → ketoconazole/aromatase inhibitors.
- Primary hypothyroidism: TSH cross-reacts with FSH-R → precocious puberty with delayed bone age (unique!) → treat with thyroxine.
- Key investigation: GnRH stimulation test distinguishes central (LH-predominant) from peripheral (suppressed) and premature thelarche (FSH-predominant).
Active Recall - Premature Puberty and Related Disorders
[1] Lecture slides: GC 149. Premature puberty puberty and related disorders.pdf (slides 1-66) [2] Senior notes: Adrian Lui Pediatrics Notes.pdf (p70) [3] Past papers: 2025 Fourth Summative MCQ.pdf (Question 77, p29) [4] Senior notes: Ryan Ho Endocrine.pdf (p73 — Congenital Adrenal Hyperplasia) [5] Senior notes: Ryan Ho Rheumatology.pdf (p171 — Neurofibromatosis type 1)