Lecture 25: Postnatal growth Flashcards
What are the 3 post-natal phases of growth?
The Karlberg model
- Infancy you achieve half your height by age 2
- Rapid Growth at birth, which declines over the first 2 years of life; less GH dependent
- So if you have a condition of an impaired liver, you will be really short as no GH
- School age
- Constant annual Growth- GH dependent!
- Adolescant
- Rapid growth primarily dependent on sex steroids and increased GH release
Humans follow a _________ gradient of growth.
From birth to puberty, the ____ grow relatively faster then other pot-cranial body segments.
Humans follow a Cephalo-caudal gradient of growth.
From birth to puberty, the legs grow relatively faster then other pot-cranial body segments.
- Why you have such a big head as a baby!
What does height velocity tell us?
Differntiates between normal short stature and pathological short stature
- Calculates over a 6-12 month interval (to reduce measurement errors), tracks over time
- ‘Normal’ HV: within 25-75th centile
Differences between girls and boys height velocities?
Girls: earlier growth spurt ~12yrs
Boys: Grow more, later ~14yrs
SO around a 2 year difference due to hormones made. Eostrogen primary driving for growth, and because girls mainly only have that they grow and fuse epipihysis earlier.
Boys also do everything but eostrogen, but can convert Testosterone to eostrogen. This takes longer, so they grow later.
The primary hormone for growth spurts?
Oestrogen!
**why boys get man boobs during puberty
Short Stature is?
- A common clinical presentation
- A symptom, or a varient (so doesn’t have to be bc of disease)
- but may indicate pathology
- Short statured people can grow with normal velocity
- Is one of the commonest manifestations of chronic illness
What’s the difference between FSS and CDGD in
Bone age
Puberty
Final Height
What is Growth Hormone secretion like and whats it increased/decreased by?
- Pulsatile with a low baseline
- Episodic and Pulsatile
- Primarily at night (stages III-IV sleep)
- So no point in measuring during the day
- Make heaps when you’re young, and decreasing with age
Increased by: sleep, exercise, stress, hypoglycaemia, aminoacids, malnutrtion, sex steroids
Decreased by: Obesity, psychosocial deprivation (kids in bad homes are short)
How does Nutrition link in with the Growth Hormone Axis?
For normal hepatic IGF-1 production you need
- Normal levels of insulin
- Normal nutrition
Malnutrition (inadequate calories) or poorly controlled diabetes (inadequate insulin) inhibits hepatic IGF-1 production.
Why liver failure ⇒ very short kids
Actions of Growth Hormones
Metabolic:
- Inhibits glucose uptake and promotes glycogenolysis (anti-insulin)
- Stimulates protein synthesis
- Promotes lipolysis
Can be endocrine, paracrine and autocrine.
Very similar receptor to insulin
Makes you make an IGF-1
IGFs (somatomedins)
- IGF-1 (somatomedin C) and IGF 2
- IGF-1 (lots of levels you go hypoglycaemic), IGF 2 and insulin (lots makes you grow) hae significant hormonology
- Each receptor has cross reactivity with the other receptors (weak)
IGF-1 Receptor Defect: live a normal life, normal fertility, just veeeeeery short: “Laron Dwarf”
Different alleles of IGF1 makes you grow different
What does eostrogen affect in terms of growth?
- Effects on skeleton and body composition
- Estrogen has a greater effect then testosterone on the skeleton!
- Responsible for epiphyseal maturation/closure in both sexes!
- If someone gave a girl the pill during her growth spurt she’ll stop growing!!!!!
- Treatment for extremely tall people
- If you can’t make estrogen you’ll keep growing! But bones will be osteoporotic and weak!
Hypothyroidism?
And what’s the role of thyroid hormones?
- You make tons of TSH → goitre
- Very malnourished, short and slow
Thyroid Hormones (Y3 an T4) have a ‘facilitatory’ role in growth
Not enough → slow growth
Too much → too fast growth
- Neccessary for normal GH secretion
- Neccessary for growth plate development
- and body proportions
So what Growth Promoting Hormones are important in the Fetus
Important:
- IGF II
- Insulin
Less important
- Human placental lactogen
- T4/3, IGF-I
**GH only has asmall role to play in growth promotion during fetal life and early infancy
IUGR: Intra uterine growth restriction
- Intra uterine growth retardation or SGA
- Very common
- Birthweight <10th centile for gestational age
- Catchup growth above the 3rd centile usually occurs by 6 months but may drag on to 2 years.
- Short stature by 2 years = indicates short final height
- DOn’t usually reach MPH
Turners Syndrome
- Missing X chromosome usually (Karyotype XO)
- abnormal/absent ovaries
- Consider in all girls with unexplained short stature of height below MPH range
- Commonest feature is short for MPH (100%)
- 50% will only have short stature as clinical feature
- can also have poor HV or delayed puberty
- Low Bone age
- Have elevated FSH and LH (primary gonadal failure)
Growth Hormone Excess: Acromegaly
- TOo much GH
- Makes you tall when you’re a kid
- Makes your jaw massive when you’re an adult
- Lots of bony overgrowth
