194b - Growth and Development Flashcards
How does linear growth rate change in:
- Primary growth disorders:
- Secondary growth disorders:
- 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
How does Cushing syndrome affect linear growth?
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
What is the major endocrine regulator of fetal growth?
Insulin
Thyroid hormone, growth hormone are important later, but not in fetal growth
Which hormone causes fusion of the growth plate at the end of puberty?
Estrogen
In people with testes, testosterone is converted to estrogen by aromatase
At what age is crossing percentile channels considered abnormal?
After 2ish years
(maybe 18 mo, but in the first year it’s okay)
List the normal growth rates (cm/year) for each age range
- 0-12 months:
- 12-24 months:
- 2 years - puberty:
- Puberty peak:
- 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!
What is the definition of short stature?
Height 2 or more standard deviations below the mean for age and sex
Does not automatically imply pathology!
What are the major endocrine regulators of growth in infancy and childhood? (2)
- 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
What causes Laron syndrome?
IGH deficiency, due to mutation in the GH receptor
Tx = give IGF-1
How does bone age compare with chronological age in:
- Primary growth disorders:
- Secondary growth disorders:
- 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
How do the hormonal changes of puberty affect linear growth?
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
How does obesity impact the secretion of growth hormone?
Obesity inhibits growth hormone secretion
How does bone age compare with chronological age in different non-pathologic causes of short stature?
- Genetic/familial:
- Constitutional delay of growth and puberty:
- Genetic/familial: Bone age = chronologic age
- Constitutional delay of growth and puberty: Bone age < chronologic age
List 4 causes of primary growth abnormalities
- Osteochondrodysplasias
- Down syndrome
- Turner syndrome
- Russel Silver syndrome
Caused by intrinsic growth plate abnormalities
Skeletal age = chronologic age
How does hypothyroidism impact puberty and growth?
What is the exception?
Hypothyroidism -> growth deceleration/failure, delayed puberty
- Exception: Van Wyk Grumbah
- Very severe primary hypothyroidism -> high TSH
- TSH stimulates LH/FSH receptor -> Puberty
