GC149 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
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)
How to read the two axis diagrams: before puberty, GnRH pulses are low and infrequent. Puberty increases their frequency and amplitude, producing pulsatile LH/FSH secretion. Oestrogen and testosterone then feed back at both hypothalamus and pituitary; downstream, both sex steroids accelerate skeletal maturation and the growth spurt through direct growth-plate effects and interaction with the GH–IGF-1 axis. The slide's dashed treatment phase illustrates how sustained GnRH-agonist exposure suppresses rather than reproduces this pulsatility. [1]
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 |
How to read the gene table on slide 8: it spans the whole axis, not just genes for early puberty. Genes affecting hypothalamic development or GnRH migration/signalling (ANOS1, FGFR1, KISS1/KISS1R, GNRHR), pituitary development (HESX1, LHX3, PROP1) or leptin/gonadotropin signalling (LEP/LEPR, FSHB/FSHR, LHB/LHCGR) usually cause delayed/absent puberty when function is lost. By contrast, activating GNAS mosaicism produces MAS and activating LHCGR variants produce FMPP. Older labels in the image include KAL1 for ANOS1 and GPR54 for KISS1R. [1]
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
The photograph shows the beads increasing stepwise in volume. Palpate each testis gently and compare it with the closest bead while excluding epididymis and scrotal skin; record right and left separately because asymmetry redirects the differential toward focal testicular disease or MAS.
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]
Current framing: retain the classic definitions (< 8 years in girls, < 9 years in boys) but do not turn the cutoff into an automatic full investigation for every isolated sign. The 2026 Endocrine Society guideline supports periodic examination rather than immediate tests for otherwise uncomplicated Tanner B2 breast development at 7–8 years, and an initial 4–6-month observation period for B2 development before 7 years when there is no rapid progression, growth acceleration or CNS symptom. [6]
Historical urban Chinese timing data shown in the deck
The two article screenshots provide useful local context, but they are cross-sectional cohorts from 2003–2005 data and should not be treated as contemporary diagnostic cutoffs: [1]
| Cohort | Slide finding |
|---|---|
| 20,654 urban Chinese girls (published 2009) | 19.57% had breast development by age 8; median B2 9.20 years, P2 11.16 years and menarche 12.27 years |
| 18,807 urban Chinese boys (published 2011) | 12.99% had testicular volume ≥4 mL by age 9; median onset by ≥4 mL was 10.55 years, P2 12.78 years and spermarche 14.05 years |
These images reinforce why age, sequence and tempo matter together. A child below the classic cutoff still needs a careful history and examination, but bone age, laboratory testing and imaging should be targeted to progression and clinical risk rather than ordered reflexively. [6]
Not all organic aetiologies and certainly not the normal variants require treatment. [1]
4. Variations of Normal Pubertal Development (deck estimate: 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 may be a relatively greater FSH than LH response, whereas CPP produces a pubertal LH response. In current practice, however, the first discriminators are tempo, growth velocity and ultrasensitive basal LH; stimulation testing is reserved for low/equivocal basal LH when suspicion persists. [6]
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 accumulates proximal to the 21-hydroxylase block, the commonest cause of CAH. For a symptomatic child beyond infancy, screen with an early-morning baseline 17-OHP using LC–MS/MS where available; if borderline, obtain a complete adrenocortical steroid profile after cosyntropin/Synacthen rather than diagnosing from an isolated nonspecific elevation. [7]
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]
The slide quotes a 15–20% later PCOS risk, especially with exaggerated adrenarche. [1]
Girls with premature adrenarche should be followed through puberty. [1]
Clinical Pearl
Premature adrenarche is usually benign and does not itself require medication. Some cohorts show increased later PCOS or metabolic risk, especially with adiposity or insulin resistance, but there is no single universal patient-level percentage. Follow growth and pubertal progression, and address weight, acanthosis and other metabolic risk factors without labelling a child as destined to develop PCOS. [11]
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 or vulvovaginitis
- Trauma or sexual abuse
- Local tumours (sarcoma botryoides / rhabdomyosarcoma of vagina)
- McCune-Albright syndrome (autonomous ovarian cysts)
- Exogenous oestrogen exposure
The evaluation must be age-appropriate, trauma-informed and alert to safeguarding concerns; “isolated premature menarche” is a diagnosis of exclusion.
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, FSH and LH are structurally related glycoprotein hormones. In severe, long-standing primary hypothyroidism, extremely high TSH can promiscuously activate FSH receptors, producing ovarian stimulation in girls or macro-orchidism in boys without the usual pubertal LH pattern (Van Wyk–Grumbach syndrome).
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]
The slide reports at least 80% idiopathic in girls versus 10% in boys. These older proportions should not be used as current individual-risk estimates. [1]
High Yield – Sex Difference in CPP Aetiology
Structural CNS causes remain more frequent in boys and in younger children, but the deck's claim that 90% of boys have a lesion is outdated. Under the 2026 Endocrine Society guideline, brain MRI is not routine for neurologically asymptomatic girls aged 6–8 or boys aged 8–9 with CPP. Younger children and anyone with headache, seizure, visual-field deficit or another CNS finding require specialist-directed neuroimaging. [6]
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: A hypothalamic hamartoma is a benign congenital malformation whose neural network can trigger premature GnRH pulsatility. It may also cause gelastic (laughing) seizures; endocrine suppression and seizure management are separate specialist decisions.
Other CNS causes of CPP:
- CNS tumours (glioma, astrocytoma, pinealoma, craniopharyngioma)
- Congenital suprasellar/midline lesions (arachnoid or Rathke cleft cyst, hydrocephalus, meningomyelocele, optic-nerve hypoplasia)
- Post-CNS infection (meningitis, encephalitis)
- Post-CNS irradiation
- Head trauma
- Perinatal CNS insult
- 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]
What the image-heavy cause table adds: match the hormone pattern to the likely source. Androgen excess may come from ovarian sex-cord stromal tumours/hyperthecosis in girls, Leydig-cell or hCG-secreting tumours in boys, or adrenal disease/exogenous anabolic steroids in either sex. Oestrogen excess in girls may reflect functional cysts, granulosa-cell tumours or MAS; rare sex-cord tumours associated with Peutz–Jeghers syndrome can cause oestrogen effects in either sex. These are prompts for targeted evaluation, not a reason for indiscriminate tumour screening. [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 |
Visual recognition from slides 42–43: the photographed MAS macules are large, irregular and jagged, with distribution that stops abruptly near the midline. The photographs are pattern-recognition aids, not diagnostic by themselves; examine the whole child for fibrous dysplasia and autonomous endocrine disease.
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 causes persistent adenylyl-cyclase activation in affected tissues. The slide calls the GTP-to-GDP step “phosphorylation”; the correct reaction is GTP hydrolysis. [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 is a somatic mosaic mutation (post-zygotic), only a subset of cells carry it. This explains the patchy, asymmetric distribution of involved skin, bone and endocrine tissue; the often sharp midline demarcation of café-au-lait pigment is a useful visual clue.
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]
The biopsy description is historical pathology teaching; testicular biopsy is not a routine diagnostic step. The modern diagnosis rests on the phenotype (disproportionate virilisation with high testosterone and suppressed gonadotropins), exclusion of hCG/tumour sources, family history and confirmatory LHCGR testing when appropriate.
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]
More precisely, inheritance is autosomal dominant with male-limited expression: females can carry and transmit an activating LHCGR variant without the childhood virilising phenotype.
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 receiving the usual pubertal FSH stimulation of seminiferous-tubule growth. Constitutively active LH receptors drive Leydig-cell testosterone production, so testicular volume is disproportionately small for the degree of penile growth and virilisation.
What the clinical photograph shows: the child is tall and markedly virilised for age, while the affected adult relative is short. This makes the time-course visible: sex steroids initially accelerate linear growth but advance bone age and close growth plates early, so untreated early tall stature can end in reduced adult height. [1]
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]
The slide lists ketoconazole as an “androgen-receptor-blocking” agent; that mechanism is incorrect. Ketoconazole inhibits steroidogenesis and has important hepatic/adrenal safety concerns. [1]
Why GnRH agonists do not treat the primary FMPP mechanism: testosterone production is gonadotropin-independent, so suppressing already-low LH/FSH does not stop autonomous LHCGR signalling. Specialist regimens may combine an antiandrogen (for example bicalutamide or spironolactone) with an aromatase inhibitor to reduce virilisation and oestrogen-mediated bone-age advancement. Evidence is limited—one open-label BATT study included only 14 boys—and these are specialist/off-label decisions with safety monitoring. Add a GnRH agonist only if secondary central puberty develops. [8]
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) |
Reading the Tanner-stage table on slide 54: [1]
| Stage | Breast | Pubic hair | Male genitalia |
|---|---|---|---|
| 1 | Prepubertal | Prepubertal | Prepubertal |
| 2 | Breast bud; nipple/areola form a small mound | Sparse, lightly pigmented hair | Testes/scrotum enlarge; scrotal skin thins/reddens; penis still prepubertal |
| 3 | Breast and areola enlarge without contour separation | Hair darkens/coarsens and spreads | Further testicular/scrotal growth; penis lengthens |
| 4 | Areola/nipple form a secondary mound | Adult-type hair but limited in area | Penis length and width increase; scrotal pigmentation; glans develops |
| 5 | Adult contour | Adult distribution | Adult size and shape |
In girls with overweight or obesity, palpate to distinguish glandular Tanner B2 tissue from lipomastia; inspection alone can over-stage thelarche. [6]
Findings suggestive of pathology: a rapid tempo of progression, advanced development, rapid linear growth, advanced skeletal maturation. [1]
6.4 Investigations
The slide lists a broad panel—LH, FSH, oestradiol/testosterone, TFT, prolactin, β-hCG, bone age, LHRH testing, pelvic ultrasound and brain MRI—but these are not all routine tests for every child. [1]
The 2026 Endocrine Society approach starts with an ultrasensitive basal LH when biochemical confirmation is needed. If basal LH is low/equivocal despite convincing or rapidly progressive clinical puberty, repeat an early-morning basal LH or perform a GnRH/GnRH-agonist stimulation test. Select sex steroids, TFTs, 17-OHP/DHEAS/testosterone, β-hCG and imaging according to the phenotype. [6]
| Investigation | What It Tells You |
|---|---|
| Ultrasensitive basal LH ± FSH | Pubertal LH supports central activation; a low value does not exclude very early CPP |
| GnRH stimulation test (LHRH test) | Next step when basal LH is low/equivocal but suspicion persists; interpret assay-specific LH response |
| Oestradiol / Testosterone | Degree of sex steroid exposure |
| TFT (TSH, T4) | Primary hypothyroidism as cause |
| Prolactin | Targeted when pituitary/stalk disease is suspected |
| β-hCG | Especially a virilised boy with suppressed LH; consider hCG-secreting germ-cell tumour/hepatoblastoma |
| Bone age X-ray (left hand/wrist) | Auxiliary measure of skeletal advancement and height risk; advancement alone does not diagnose CPP [6] |
| Pelvic USG | Auxiliary assessment of uterine/ovarian oestrogen effect and cyst/mass; operator-dependent and not diagnostic alone |
| MRI brain | Targeted by age and CNS findings; not routine in neurologically asymptomatic girls 6–8 or boys 8–9 with CPP [6] |
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 |
| Presentation | Discriminating pattern | Main interpretation / next step |
|---|---|---|
| Girl with pubarche only | Rapid growth + markedly advanced bone age; raised testosterone, 17-OHP or DHEAS | Investigate CAH/NCAH, adrenal tumour, ovarian source, or exogenous androgen with adrenal/pelvic imaging as indicated |
| Girl with pubarche only, age 5–7 | Normal growth, only mildly advanced bone age, prepubertal testosterone/normal 17-OHP with possible pubertal DHEAS | Idiopathic premature adrenarche |
| Girl with thelarche only | Normal growth, non-advanced bone age, prepubertal LH/FSH | Idiopathic premature thelarche |
| Girl with thelarche only | Rapid growth + advanced bone age, prepubertal LH/FSH but pubertal oestradiol | Peripheral oestrogen source: consider McCune–Albright syndrome, ovarian pathology, or exogenous oestrogen |
| Girl with thelarche + pubarche | Pubertal LH/FSH and oestradiol | Central precocious puberty; MRI depends on age/CNS findings [6] |
| Boy with virilisation and bilaterally small/prepubertal testes | Suppressed LH/FSH with raised testosterone ± raised 17-OHP | Extra-testicular androgen source: CAH/NCAH, adrenal tumour, or exogenous testosterone |
| Boy with asymmetric testes | Suppressed LH/FSH with pubertal testosterone | Testicular ultrasound for a functioning testicular tumour |
| Boy with bilateral testicular enlargement | Pubertal gonadotropins | Central precocious puberty; MRI depends on age/CNS findings [6] |
| Boy with small testes, suppressed gonadotropins and very high testosterone | Check β-hCG; if negative consider autonomous testicular function | hCG-secreting tumour if β-hCG is raised; FMPP or McCune–Albright syndrome if β-hCG is undetectable |
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]
The slide gives 4-weekly depot IM leuprolide as the usual regimen. [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.
Monthly leuprolide remains one option, but it is no longer the only default. Several longer-acting injectable/implant formulations exist; the 2026 guideline suggests starting with the formulation expected to be used long term rather than automatically beginning with a monthly injection. Choice depends on availability, licensed dosing, adherence, procedures, cost and family preference. [6]
Who Benefits Most?
The age bands on the slide are a useful historical heuristic, not automatic treatment rules. Current decision-making weighs documented tempo, growth velocity, bone-age advancement, predicted-height loss, stage relative to peak growth, likely age at menarche, psychosocial context and family preferences. A 4–6-month observation period often distinguishes slowly from rapidly progressive disease. Girls aged 7–8 with slowly progressive CPP and children already at/past peak pubertal growth are less likely to gain meaningful height; rapidly progressive CPP is more likely to benefit. [6]
Treatment depends on the cause: [1]
- Surgical removal of tumours ± chemotherapy and/or radiation therapy as indicated
- Large ovarian cysts: drainage under USG guidance (an older blanket statement; not routine current management)
- Exogenous oestrogens or androgens: should be uncovered and eliminated
- Non-classical CAH: exogenous glucocorticoid (only for selected symptomatic/progressive patients)
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.
Safety updates: functional ovarian cysts are commonly observed with serial clinical/ultrasound review; in MAS, ovarian surgery should generally be avoided, with intervention reserved for torsion risk or another compelling expert-defined indication. [9] For non-classic CAH, glucocorticoids are suggested in children/adolescents with inappropriately early and rapidly progressive pubarche/bone-age advancement or overt virilisation—not for asymptomatic patients. [7]
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 → suspected central precocious puberty → ultrasensitive basal LH first, stimulation if needed; young age supports MRI
- Vignette: 3-year-old boy with enlarged penis, pubic hair, but small testes → peripheral cause; use testosterone, LH/FSH, 17-OHP/DHEAS and β-hCG to distinguish adrenal disease, hCG stimulation, exposure or autonomous testicular function
- Vignette: Girl with café-au-lait spots with "coast of Maine" borders + vaginal bleeding + bone pain → McCune-Albright syndrome
- Vignette: Boy aged 4 with disproportionate virilisation, high testosterone, suppressed gonadotropins and a family history → FMPP → specialist antiandrogen plus aromatase-inhibitor therapy may be used; GnRH agonist only for secondary CPP
| 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!) |
| Treating MRI as automatic for every boy | Current guidance avoids routine MRI in asymptomatic boys aged 8–9; image younger boys and anyone with CNS findings according to specialist/local protocol [6] |
| 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: start with ultrasensitive basal LH when biochemical confirmation is needed; add sex steroids and phenotype-directed tests, bone age, stimulation testing or imaging as indicated.
- A pubertal LH pattern supports central precocious puberty; MRI is targeted by age and neurological findings rather than automatic in every older asymptomatic child. [6]
- Treat rapidly progressive CPP when likely benefit exceeds burden; use the GnRH-agonist formulation expected for long-term therapy and monitor clinically. [6]
High Yield Summary
- Precocious puberty = pubertal signs < 8 years in girls or < 9 years in boys.
- An isolated, non-progressive sign may be a normal variant; document growth and Tanner stage over time rather than assuming every child needs the same test panel.
- Central precocious puberty activates the HPG axis: start with ultrasensitive basal LH, stimulate if equivocal, and target MRI by age/CNS findings. Treat likely-beneficial progressive disease with a suitable GnRH-agonist formulation. [6]
- Peripheral precocious puberty shows sex-steroid effects with suppressed gonadotropins: investigate the ovarian, testicular, adrenal, hCG, exogenous or genetic source and treat that cause.
- McCune-Albright: café-au-lait "coast of Maine" + fibrous dysplasia + autonomous endocrinopathy; somatic Gsα mutation.
- Familial testotoxicosis (FMPP): autosomal-dominant LHCGR activation with male-limited expression; specialist antiandrogen plus aromatase-inhibitor therapy may be used, with GnRH agonist only if secondary CPP develops. [8]
- Primary hypothyroidism: TSH cross-reacts with FSH-R → precocious puberty with delayed bone age (unique!) → treat with thyroxine.
- Biochemical sequence: ultrasensitive basal LH first; if low/equivocal despite convincing clinical progression, repeat early-morning LH or use GnRH/GnRH-agonist stimulation. [6]
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) [6] Endocrine Society. Central precocious puberty: an Endocrine Society clinical practice guideline (2026; co-sponsored by AAP, ESPE and PES) [7] Endocrine Society. Congenital Adrenal Hyperplasia Due to Steroid 21-Hydroxylase Deficiency: Clinical Practice Guideline (2018) [8] Reiter EO, et al. Bicalutamide plus anastrozole for testotoxicosis: phase II open-label BATT study (2010) [9] FD/MAS International Consortium. Best practice management guidelines for fibrous dysplasia/McCune–Albright syndrome (2019) [10] Aarhus International Turner Syndrome Meeting. Clinical practice guidelines for the care of girls and women with Turner syndrome (2024) [11] Pediatric Endocrine Society/AAP Section on Endocrinology. Premature Adrenarche: A Guide for Families
GC148 Neurological Examination In Neonates, Infants, And Young Children, Including Those With Neurological Diseases
A systematic age-appropriate assessment of mental status, cranial nerves, tone, posture, primitive reflexes, developmental milestones, and motor function in young children to detect and characterize neurological abnormalities.
GC150 The Child Is Too Thin Nutrition And Growth, Nutritional Deficiency States
Nutritional deficiency states in children presenting with excessive thinness result from inadequate caloric or nutrient intake leading to impaired growth, wasting, and conditions such as marasmus or kwashiorkor.