Growth is not just "getting bigger." It reflects the integrated function of genetics, hormones, nutrition, organ systems, and psychosocial well-being. A child who stops growing or deviates from their expected trajectory is essentially telling you something is wrong—long before other symptoms appear. This is why serial plotting on growth charts is the single most important surveillance tool in paediatrics.

Growth is an orchestrated network of control—it cannot be too much, cannot be too little, and must happen at the right time and right place. ^[1]

The opening images (small and large animals and fruit, followed by conception → fetus → newborn) make two points: normal size varies, and growth begins prenatally. Size is determined by:

1. Genetic potential – parental heights set the "target"
2. Hormonal milieu – GH, thyroid hormone, sex steroids, cortisol, insulin/IGF-1
3. Nutrition – calories, protein, micronutrients
4. Health/disease – chronic illness diverts energy from growth
5. Psychosocial environment – deprivation and stress suppress GH secretion

Why this matters: In fetal life, maternal, placental and environmental factors strongly influence size. After birth, many children show physiological catch-up or catch-down toward their genetic channel during the first 2–3 years. Persistent centile crossing after that age, or impaired height velocity at any age, is more concerning.

Normal growth is the progression of changes in weight, height, and head circumference that are compatible with established standards for a given population, reflecting genetic potentials and environmental factors, with adequate lengthening of the skeleton. ^[1]

A newborn's size is determined by the intrauterine environment—influenced by maternal size, nutrition, general health, and social habits (e.g., smoking status). ^[1]

This is why birth weight correlates more with maternal size than paternal size. A genetically tall baby born to a small mother will be constrained in utero but will "catch up" postnatally.

Growth velocity is greatest in late fetal life, then peaks again during puberty, and eventually decreases when oestrogen-mediated epiphyseal fusion occurs in adolescence. ^[1]

Key point: It is oestrogen (not testosterone) that causes epiphyseal fusion in both sexes. Boys grow taller than girls partly because they enter puberty ~2 years later, giving them more years of pre-pubertal growth at ~5 cm/year.

Growth rates are similar between genders until puberty. Males have a later pubertal growth spurt and higher velocity during the spurt. ^[1]

Growth-velocity graph: velocity is highest in infancy, falls rapidly toward a prepubertal plateau of roughly 5–6 cm/year, then rises again at puberty. The female curve shifts earlier; the male curve peaks later and slightly higher. Interpret the curve against Tanner stage rather than expecting every child to peak at the labelled mean age.

Hong Kong-specific context:

The deck quotes 50th-centile adult heights of 171 cm for males and 158 cm for females from its historical Hong Kong reference. Treat these as slide-era figures, not timeless constants. For current clinical plotting, use the sex- and age-specific Hong Kong 2020 Growth References (HK2020). ^[1][8]

1. Use the correct sex, age and locally adopted reference; measure supine length in infants and standing height in older children, then plot the exact value.
2. Interpret position and trajectory together. A stable low centile can be normal; falling across centile channels after early catch-down suggests reduced velocity.
3. Compare height with weight/BMI and parental target height. Disproportionate change provides a clue to mechanism.
4. In children with a condition that has a distinct growth pattern (for example Down syndrome or achondroplasia), use the relevant condition-specific chart alongside the general chart.
5. A centile is a rank, not a diagnosis. Measurement error, technique and interval between measurements must be checked before initiating a work-up.

Average length at birth for a term infant is 50 cm (20 inches). ^[1]

The deck uses the rough heuristic that children reach about one-half of adult height by 24–30 months. ^[1]

Example from the lecture: Ethan is 86 cm at 24 months → 86 × 2 ≈ 172 cm. This is a memory aid, not a valid individual adult-height prediction; use serial growth, parental target height, pubertal timing and, when indicated, bone-age prediction.

Cumulative Length/Height Milestones [1]

*The 12-year value varies substantially with pubertal timing. These are slide-derived round-number anchors, not diagnostic cut-offs.

Boy = (father's height + mother's height + 13) ÷ 2 Girl = (father's height + mother's height − 13) ÷ 2 ^[1]

The ±13 cm adjusts for the average height difference between adult males and females. The target range is MPH ± 8.5 cm (approximately 3rd to 97th centile for that family).

Example from lecture:

Ethan: Mother 164 cm, Father 170 cm → MPH = (164 + 170 + 13)/2 = 173 cm ^[1]

Though not heavily detailed in this lecture, head circumference is the third key growth parameter. It reflects brain growth. In failure to thrive, weight drops first, then height, with relative sparing of head circumference (the body protects brain growth). If head circumference is disproportionately affected, think of a primary neurological/genetic problem rather than nutritional failure.

Short stature is commonly defined as height ≤ −2 SD for age, sex and reference population. ^[1]

Mathematically, −2 SD is approximately the 2.3rd centile, so clinical resources often operationalise it as below the 3rd centile. The exact plotted value, velocity, distance from parental target height and clinical context matter more than whether a chart labels the lower line “2nd” or “3rd.” ^[10]

1. How short is the child? 2. Is the child's height velocity impaired? 3. What is the child's predicted adult height? ^[1]

Height velocity is more important than a single height measurement. A child on the 5th centile who is growing at a normal velocity along that centile is likely a normal variant. A child on the 25th centile whose growth is crossing downward is more concerning.

P – Psychological deprivation I – Iatrogenic (glucocorticoids, spinal radiation) C – Chronic illness N – Nutritional I – Intrauterine growth restriction / born small for gestational age without catch-up (including Silver–Russell syndrome) C – Chromosomal (Turner, Noonan, Down, Prader-Willi) S – Skeletal dysplasia (achondroplasia, hypochondroplasia) ^[1]

Plus Endocrine causes: hypothyroidism, GH deficiency, Cushing syndrome.

This is the lecture's core pattern-recognition framework:

1. Dysmorphism with a recognizable syndrome 2. Disproportionate short stature – usually needs a skeletal survey 3. Short but thin – search for chronic illness 4. Short and fat – more suggestive of an endocrine cause ^[1]

Body height < 1st centile; abnormally short for family heights; history or examination suggestive of chronic illness; abnormal growth velocity; abnormal body proportions; dysmorphic features or midline defects. ^[1]

Search for associated chronic disease: cardiovascular disease, respiratory disease (cystic fibrosis), malabsorption/chronic inflammatory bowel disease, chronic renal failure, psychosocial deprivation, anorexia nervosa. ^[1]

The image pair links chronic kidney disease (CKD) with growth failure and bowed legs from CKD–mineral and bone disorder (“renal rickets”). The thalassaemia photograph illustrates historical marrow-expansion facies; current growth impairment more often reflects the combined effects of chronic anaemia, transfusional iron overload, endocrine complications and treatment burden.

Why short AND thin? The chronic illness consumes energy reserves → weight drops first (thin), then linear growth suffers (short). This is the opposite pattern to endocrine causes.

More suggestive of endocrine cause: panhypopituitarism, isolated growth hormone deficiency, hypothyroidism, pseudohypoparathyroidism, Cushing's syndrome, Prader-Willi syndrome. ^[1]

Why short AND fat?

• GH deficiency: GH promotes lipolysis and linear growth. Without it, fat accumulates and bones don't grow.
• Hypothyroidism: Thyroid hormone is essential for normal bone maturation and metabolism. Low TH → slow metabolism (fat gain) + delayed bone age (short).
• Cushing's syndrome: Excess cortisol promotes central adiposity and inhibits GH secretion and growth plate activity.

The hypothyroidism and Cushing syndrome photographs demonstrate the pattern of poor linear growth with preserved/increased weight; body shape alone cannot distinguish these disorders—history, growth velocity, examination and biochemical testing do.

Pseudohypoparathyroidism / Albright hereditary osteodystrophy image: brachydactyly from shortened metacarpals—classically the fourth and/or fifth—causes a “knuckle–knuckle–dimple–knuckle” pattern when the fist is made. Confirm the biochemical and genetic diagnosis; the hand sign is not specific by itself.

Prader–Willi syndrome: the natural history is the important clue: marked neonatal hypotonia and feeding difficulty followed later by hyperphagia and obesity, with short stature/GH-axis dysfunction, hypogonadism, developmental/behavioural differences and small hands/feet. The facial features shown on the slide are variable and should not be used alone to diagnose the condition.

Two normal variants: Familial short stature and Constitutional delay. ^[1]

• Tall parents; growth is usually stable and appropriate to target height
• Early puberty is a separate possible contributor to apparent tallness
• Bone age may be advanced and can inform, but not precisely guarantee, predicted final height

Hyperthyroidism; Precocious puberty (tall at diagnosis but reduced final height due to premature fusion of epiphyses); GH-secreting tumours (extremely rare in paediatrics). ^[1]

Why is precocious puberty a cause of TALL stature initially but SHORT final height? Early puberty → early sex steroid exposure → early growth spurt (child is temporarily tall for age) → but also early epiphyseal fusion → growth stops prematurely → reduced adult height.

BMI is the widely accepted standard measure of overweight and obesity for children ≥ 2 years. ^[1]

In children, absolute BMI changes with age, so use the adopted age- and sex-specific reference, not adult cut-offs:

The adult Asian thresholds shown on slide 65 apply at adulthood, not to younger children. BMI is a screening measure rather than a direct measurement of adiposity, so interpret it with trajectory, body composition, pubertal stage and clinical context. In infants, use weight-for-length or the locally adopted infant standard.

The circular diagram deliberately shows interacting determinants rather than a single cause: genetics/epigenetics, early-life events, biology, environment, stress and behaviour. ^[1]

Childhood obesity is a complex chronic disease shaped by these interacting influences. Endocrine causes are uncommon; reduced height velocity is the clue that should prompt targeted endocrine evaluation. Rapid-onset severe obesity in early childhood, hyperphagia, developmental differences or dysmorphism should raise concern for hypothalamic, monogenic or syndromic disease.

The organ-system diagram explains why assessment must go beyond the BMI number. Ask about sleep and psychosocial health; measure blood pressure; examine for hepatomegaly, acanthosis nigricans, pubertal/endocrine clues and orthopaedic pain or limp. In the AAP guideline, children aged ≥10 years with obesity are evaluated for lipid abnormalities, abnormal glucose metabolism and abnormal liver function; local protocols may differ. ^[16]

The slide cites high rates of metabolic syndrome and dysglycaemia in selected cohorts and correctly stresses that youth-onset T2DM can show rapid β-cell decline. However, these cohort percentages are not universal screening-test probabilities and should not be applied to an individual child without context.

Hong Kong epidemiological data: The slide's primary-school graph (2013/14–2022/23) shows boys consistently above girls and an overall peak of 20.6% in 2021/22. Because COVID-era service disruption changed the number and pattern of attendees, direct comparison across affected years is limited. The Department of Health subsequently reported overweight (including obesity) among 16.4% of attending primary students and 20.0% of attending secondary students in 2023/24, using its Student Health Service definition; these are detection rates among attendees, not necessarily population prevalence. ^[1][17]

How to read the Kaplan–Meier plot on slide 72: in one historical cohort diagnosed at age 15–30 years, the T2DM group had lower cumulative survival than the T1DM group (reported hazard ratio 2.0, 95% CI 1.2–3.2). This supports the seriousness of youth-onset T2DM but does not mean every young person with T2DM has the survival percentages read from the far end of this small cohort's curve. ^[1]