Growth and Puberty 1

Question 1

What are the four phases of normal human growth?

Answer 1

1) Fetal phase
2) Infantile phase
3) Childhood phase
4) Pubertal growth spurt

Question 2

What is meant by “failure to thrive”?

Answer 2

An inadequate rate of weight gain during the infantile phase

Question 3

What determines size at birth?

Answer 3

The size of the mother and the placental nutrient supply, which in turn modulates fetal growth factors such as IGF2, human placental lactogen and insulin

Question 4

Size at birth is largely independent of which factors?

Answer 4

Fathers height and growth hormone

Question 5

How does birth weight affect later metabolic risk of childhood obesity?

Answer 5

Low birth weight, paradoxically, increases the risk

Question 6

What period constitutes the infantile phase of growth?

Answer 6

From birth to around 18 months

Question 7

What factors is growth during the infantile phase largely dependent on?

Answer 7

Adequate nutrition, good health and normal thyroid function

Question 8

What % of eventual height does the fetal phase account for?

Answer 8

30% - fetal phase is the fastest period of growth

Question 9

What % of eventual height does the infantile phase account for?

Answer 9

15%

Question 10

What % of eventual height does the childhood phase account for?

Answer 10

40% (slow, steady prolonged period of growth)

Question 11

What is the main determinant of a child’s rate of growth during the childhood phase (provided there is adequate nutrition & good health)?

Answer 11

The main determinant is pituitary growth hormone secretion acting to produce IGF-1 at the epiphyses. But thyroid hormone, vitamin D and steroids also affect cartilage cell division and bone formation.

Question 12

What is psychosocial short stature?

Answer 12

Profound chronic unhappiness can lead to a reduction in growth hormone secretion and thus cause short stature (rare)

Question 13

What % of eventual height does the pubertal growth spurt contribute and how?

Answer 13

During the pubertal growth spurt, sex hormones testosterone and oestradiol cause the back to lengthen and boost GH secretion. This adds 15% to final height.

Question 14

What other action do the sex steroids have on growth?

Answer 14

They also cause fusion of the epiphyseal growth plates and cessation of growth

Question 15

What happens to growth if puberty is early?

Answer 15

If puberty is early final height is reduced because of early fusion of the epiphyseal growth plates. (Not uncommon in girls).

Question 16

What measurements are used to monitor growth?

Answer 16

Weight, height and head circumference

in children up to 2 years, length is used

Question 17

How and why is head circumference measured?

Answer 17

You measure the occipitofrontal circumference to measure head and hence brain growth. Three measurements should be done and the maximum of the three recorded. It is of particular importance in developmental delay or suspected hydrocephalus.

Question 18

How does weight differ between totally breast fed babies compared with bottle-fed babies?

Answer 18

Breast fed babies tend to have lower weight

Question 19

What is classified as a significant abnormality of height?

Answer 19

• Measurements outside the 0.4th or 99.6th centile if the mid parental height is not short or tall
• If height is markedly discrepant from weight
• Serial measurements which cross growth centile lines after the first year of life

Question 20

How was puberty changed in girls over the last twenty years?

Answer 20

The mean age at which puberty starts has lowered, but the age at which girls have their first period has remained stable - so females now remain in puberty for longer.

Question 21

What is the first feature of female puberty and when does it occur?

Answer 21

Breast development which usually starts between about 8.5 and 12.5 years

Question 22

What is the second stage of puberty in females?

Answer 22

Pubic hair growth and rapid height spurt - occurring almost immediately after breast development

Question 23

When does menarche (the first period) tend to occur and what does it signal?

Answer 23

On average 2 and a half years after the start of puberty. It signals that growth is coming to an end with only around 5cm height gain remaining

Question 24

What is the first sign of male puberty?

Answer 24

Testicular enlargement to >4ml volume (measured using an orchidometer)

Question 25

What is the second stage of puberty in males?

Answer 25

Pubic hair growth - usually occurs between 10 and 14 years of age.

Question 26

What is the final stage of puberty in males?

Answer 26

Height spurt - this occurs when the testicular volume is around 12-15 ml (after a delay of around 18 months from the start of puberty)

Question 27

How can puberty be assessed if abnormally early or late?

Answer 27

• An x-ray can be done to look at bone age measurements and determine skeletal maturation
• In girls a pelvic USS can be used to assess uterine size and endometrial thickness

Question 28

What can be considered normal menstrual cycle length in teens?

Answer 28

Theres a wide range of normal variation and cycle length can be anything from 21 days to 45 days

Question 29

Define short stature

Answer 29

A height below the second centile (i.e. 2 SDs below the mean) or the 0.4th centile (2.6 SDs below the mean)

Question 30

How many children will be shorter than the 2nd and 0.4th centiles?

Answer 30

1 in 50 children will be shorter than the second centile and 1 in 250 will be shorter than the 0.4th centile

Question 31

How can growth failure be recognised when the height still lies within the normal distribution?

Answer 31

By measuring height velocity. Two accurate measurements at least 6 months (but preferably a year) apart allow height velocity to be calculated in cm/year. A height velocity persistently below the 25th centile is abnormal and that child will eventually become short.

Question 32

What is a disadvantage of height-velocity calculations?

Answer 32

They are highly dependent on the accuracy of height measurements

Question 33

How is the mid-parental target height calculated for boys and girls

Answer 33

It is the mean of father’s and mother’s height with 7cm added for boys and 7cm subtracted for girls

Question 34

How does intrauterine growth restriction (IUGR) and extreme prematurity affect height?

Answer 34

About one third of children born with intrauterine growth restriction or were extremely premature remain short and growth hormone treatment may be indicated

Question 35

What is constitutional delay of puberty?

Answer 35

Constitutional delay in puberty is a normal variation in the timing of puberty. These children have delayed puberty which is often familial, having occurred in the parent of the same sex. Or it may also be induced by dieting or excessive physical training.

Question 36

Which sex is a constitutional delay in puberty more common in?

Answer 36

Males

Question 37

What are the endocrine causes of short stature? What are they associated with?

Answer 37

Hypothyroidism, GH deficiency, IGF-1 deficiency and steroid excess - these are all uncommon causes of short stature
They are associated with children being relatively overweight i.e. their weight is on a higher centile than their height

Question 38

What is the usual cause of hypothyroidism leading to growth failure?

Answer 38

Autoimmune thyroiditis.
(Not congenital hypothyroidism as this is diagnosed soon after birth by screening and so does not result in any abnormality of growth).

Question 39

What are the possible causes of a growth hormone deficiency?

Answer 39

Abnormal pituitary function which may be cause by: congenital midfacial defects; a craniopharyngioma; a hypothalamic tumors or trauma such as head injury, meningitis and cranial irradiation.

Question 40

What is craniopharyngioma? (crane-ee-o-far-inge-ee-oma) and how does it present?

Answer 40

A type of brain tumour derived from pituitary embryonic tissue. They tend to present in late childhood and may results in abnormal visual fields(characteristically a bitemporal hemianopia), optic atrophy or papilloedema on fundoscopy.

Question 41

How does growth hormone deficiency affect the bone age?

Answer 41

Bone age is markedly delayed

Question 42

What is Laron syndrome? And what do investigations show in these patients?

Answer 42

Laron syndrome is a condition caused by defective growth hormone receptors resulting in growth hormone insensitivity. Investigations show high growth hormone levels but low IGF1 levels

Question 43

Where is IGF-1 produced?

Answer 43

At the growth plate and in the liver

Question 44

Inadequate nutrition and chronic illnesses can cause short stature. Name three conditions where this may be the case.

Answer 44

Coeliac disease
Crohns disease
Chronic renal failure

Question 45

Name four chromosomal disorders associated with short stature

Answer 45

Turners syndrome, Noonan syndrome, Russel-Silver syndrome, Down’s syndrome
(Acronym: Turn the Noise Right Down!)

Question 46

Extreme short stature is caused by absolute resistance to growth hormone. Which two conditions is this seen in?

Answer 46

Laron syndrome and primordial dwarfism

Question 47

What gene is responsible for short stature in Turners syndrome and tall stature in Klinefelter syndrome and how?

Answer 47

The short stature homeobox (SHOX) gene. In Turners syndrome there is a copy of the gene missing and in Klinefelter syndrome there is additional copies of the gene

Question 48

What measurements can be carried out to confirm disproportionate short stature?

Answer 48

1) Sitting height - measures base of spine to top of head
2) Subischial leg length - measured by subtraction of sitting height from total height
3) Limited radiographic skeletal survey to identify the skeletal abnormality

Question 49

What is achondroplasia?

Answer 49

A form of short limb dwarfism

Question 50

What may cause the back to be disporoportionately short?

Answer 50

Scoliosis and some storage disorders such as the mucopolysaccharidoses

Question 51

What are the indications for growth hormone treatment?

Answer 51

Growth hormone deficiency; Turners syndrome; Prader-Willi syndrome; Chronic renal failure; SHOX deficiency and intrauterine growth restriction.

Question 52

What can be used to treat Laron syndrome?

Answer 52

Recombinant IGF1 (new, very expensive treatment)

Question 53

Name three endocrine causes of tall stature

Answer 53

Hyperthyroidism
Congenital adrenal hyperplasia
True gigantism (excess GH)

Question 54

Describe normal head growth

Answer 54

Most head growth occurs in the first 2 years of life and 80% of adult head sized is achieved by age 5. This largely reflects brain growth but small or large heads may be familial and the mid parental head percentile may need to be calculated.

Question 55

When do the fontanelle close?

Answer 55

The posterior fontanelle (lambda) has closed by 8 weeks and the anterior fontanelle (bregma) closes between 12 and 18 months.

Question 56

Define microcephaly

Answer 56

A head circumference below the 2nd centile

Question 57

What are the causes of microcephaly?

Answer 57

1) Familial - when it is present from birth and development is often normal
2) An autosomal recessive condition - when it is associated with developmental delay
3) Caused by a congenital infection
4) Caused by insult to the developing brain such as perinatal hypoxia, hypoglycaemia or meningitis (when it is often accompanied by cerebral palsy and seizures).

Question 58

Define macrocephaly

Answer 58

A head circumference above the 98th centile (most are normal children and often the parents have large heads)

Question 59

What must be suspected if rapidly increasing head circumference?

Answer 59

Raised intracranial pressure which could be due to hydrocephalus, subdural haematoma or a brain tumour.

Question 60

How would you investigate a rapidly increasing head circumference

Answer 60

By intracranial USS if the anterior fontanelle is still open. Otherwise, head CT or MRI.

Question 61

What is occipital plagiocephaly and why has it’s incidence increased?

Answer 61

It’s positional moulding, usually causing flattening of the back of the head by lying babies on their back - it has increased in recent times due to the advice given to parents to lie their baby on their back to sleep to reduce the risk of sudden infant death syndrome.

Question 62

Define craniosynostosis

Answer 62

Premature fusion of one or more sutures of the head (which can lead to distortion of head shape).