194b - Growth and Development

Question 1

How does linear growth rate change in:

• Primary growth disorders:
• Secondary growth disorders:

Answer 1

• Primary growth disorders: Linear growth rate may be normal
  
  • ​Intrinsic changes at growth plate (ex: achondroplasia)
  • Bone age = chronologic age
• Secondary growth disorders: Linear growth rate will be slow
  
  • ​Usually secondary to an endocrine abnormality
  • Bone age < chronologic age

Question 2

How does Cushing syndrome affect linear growth?

Answer 2

Cushing = elevated cortisol -> suppressed linear growth

• Suppresses GH and IGF-1 action at the growth plate
• Will also cause:
  
  • Central obesity
  • “buffalo hump”
  • Purple/red abdominal striae
  • Round face
  • Easy bruising
  • Osteopenia
  • Depression

Question 3

What is the major endocrine regulator of fetal growth?

Answer 3

Insulin

Thyroid hormone, growth hormone are important later, but not in fetal growth

Question 4

Which hormone causes fusion of the growth plate at the end of puberty?

Answer 4

Estrogen

In people with testes, testosterone is converted to estrogen by aromatase

Question 5

At what age is crossing percentile channels considered abnormal?

Answer 5

After 2ish years

(maybe 18 mo, but in the first year it’s okay)

Question 6

List the normal growth rates (cm/year) for each age range

• 0-12 months:
• 12-24 months:
• 2 years - puberty:
• Puberty peak:

Answer 6

• 0-12 months: 25 cm/year
• 12-24 months: 12.5 cm/year
• 2 years - puberty: 6-8 cm/year
• Puberty peak: 9-10 cm/year

First year of life = fastest growth rate!

Question 7

What is the definition of short stature?

Answer 7

Height 2 or more standard deviations below the mean for age and sex

Does not automatically imply pathology!

Question 8

What are the major endocrine regulators of growth in infancy and childhood? (2)

Answer 8

• Growth hormone
  
  • Affects bone, muscle, adipose tissue, linear growth
  • Primary function = linear growth
• Thyroid hormone
  
  • Bones! TH directly affects epiphyseal cartilage
  • Permissive effect on GH secretion

Question 9

What causes Laron syndrome?

Answer 9

IGH deficiency, due to mutation in the GH receptor

Tx = give IGF-1

Question 10

How does bone age compare with chronological age in:

• Primary growth disorders:
• Secondary growth disorders:

Answer 10

• Primary growth disorders: Bone age = chronologic age
  
  • ​Intrinsic changes at growth plate (ex: achondroplasia)
  • Linear growth rate may be normal
• Secondary growth disorders: Bone age < chronologic age
  
  • ​Usually secondary to an endocrine abnormality
  • Linear growth rate will be slow

Question 11

How do the hormonal changes of puberty affect linear growth?

Answer 11

Puberty -> increased testosterone and estrogen

• Both stimualte GH secretion from the pituitary
• Estrogen inhibits the negative feedback of IGF-1 on the pituitary
  
  • Prevents increasing IGF-1 from inhibiting GH secretion -> more GH secretion
• Estrogen causes maturation and fusion of the growth plate
  
  • So eventually, will halt linear growth

The main function of GH during childhood/puberty is to promote linear growth

Question 12

How does obesity impact the secretion of growth hormone?

Answer 12

Obesity inhibits growth hormone secretion

Question 13

How does bone age compare with chronological age in different non-pathologic causes of short stature?

• Genetic/familial:
• Constitutional delay of growth and puberty:

Answer 13

• Genetic/familial: Bone age = chronologic age
• Constitutional delay of growth and puberty: Bone age < chronologic age

Question 14

List 4 causes of primary growth abnormalities

Answer 14

• Osteochondrodysplasias
• Down syndrome
• Turner syndrome
• Russel Silver syndrome

Caused by intrinsic growth plate abnormalities

Skeletal age = chronologic age

Question 15

How does hypothyroidism impact puberty and growth?

What is the exception?

Answer 15

Hypothyroidism -> growth deceleration/failure, delayed puberty

• Exception: Van Wyk Grumbah
  
  • Very severe primary hypothyroidism -> high TSH
  • TSH stimulates LH/FSH receptor -> Puberty

Question 16

What is the primary function of growth hormone in childhood?

Answer 16

Promote linear growth

• Direct effect on the bone
• Indirect effect via stimulation of IGF-1 production