Lecture 23: Post Natal Growth Flashcards
What are the factors that effect normal somatic growth in childhood
- Chronic conditions, genetic/chromosomal abnormalities
- Hormonal balance
- Adequate nutrition and non deprivation - (psychosocial dwarfism)
Can you compare the rates of growth in infancy, childhood and puberty and hormones influences this
- Infancy (-> 2yrs) : rapid rate of growth at birth which declines quickly over the first two years of life.
- IGF-2, insulin, PDGF, EGF, FGF dependent (not rlly GH) - Childhood - constant linear growth
- GH, IGF-1 and T4,3 dependent, - Puberty: Rapid growth primarily dependent on
- Sex steroid, Insulin, GH, T4,3 IGF-1
How does the proportion of the body change from embryo to puberty
- Cephalo-> caudal gradient of growth
where embryo goes from 1/2 head to 1/8th head and 1/2 legs in puberty this is because from birth the legs grow relatively faster than other post cranial body segments
What is the effect of Growth hormone (anabolic), when is it secreted
Too much in childhood= gigantism, in adults growing plates stopped so acromegaly
+ effect on wellbeing. Stimulating liver to make IGF-1
- Inhibits glucose uptake and promotes glycogenolysis, promotes lipolysis for energy
- Decreases fat mass - Stimulates protein synthesis
- Increases muscle mass - IGF-1 stimulates receptors on prechondrocytes in the epiphyseal growth plate in long bones to differentiate and produce their own IGF-1 driving them to maturity
- Bone strength
Pulsatile secretion at a low baseline primarily at night in stages 3-4 of sleep so mostly looks like 0.
What increases (8) and decreases (3) GH secretion
Increased
- sleep,
- exercise, stress, hypoglycaemia, malnutrition
- amino acids, sex steroids
Decreased by
- obesity, psychosocial deprivation, excess glucocorticoids
Is GH an endocrine, paracrine or autocrine hormone?
what about IGF-1
GH All three:
- Endocrine effects are the main (from pit)
- Paracrine/Autocrine - tissues making their own is in cancer
IGF-1 is principally endocrine in the liver but paracine/autocrine in the bone.
What are the clinical signs of GH deficiency in children
- Abnormally slow height velocity- don’t have to be short
- increased abdo adiposity
- in babies they can have hypoglycaemia or small penis
How is GH deficiency tested for (3 steps)/ GH measured and when is it not accurate
- 1st look at height velocity:
if above 25%ile (to 75th) there is no growth failure so hormone milieu is adequate - IGF-1 levels measured: (random GH is not helpful)
* But GH can be high even though IGF-1 production is inhibited by insulin or inadequate nutrition or insulin- opposite for obese children so not always accurate - Formal testing requires stimulation test where in the clinic IV medications
- (arginine (AA),
- clonidine (sleepy),
- insulin (hypoglycaemia),
that induce GH secretion are given and peak response is measured
What is Laron dwarfism
Defective GH receptor so GH doesn’t work in their body. They almost never get cancer
What is IGF-1 (insulin like GF-1) and its role in growth compared to Insulin
IGF: Major post natal GF, majority bound to BP-3 binding protein.
Insulin: is faciliatory providing substrate for growth
Both
Promotes glucose, lipid, amino acid uptake for cell proliferation and differentiation.
What is the effect of Estrogen on growth/ what happens if it isn’t there/not able to be made
Skeleton: Maturation and closure of epiphyseal plates in both sexes (more than T2 as T2->E2). If no estrogen then won’t stop growing
What is the role of thyroid hormones in growth what happens if it isn’t there/not able to be made
T3 and T4 is necessary for normal GH secretion and growth plate development.
Hypothyroidism causes growth failure - slow down and stop
with delay of maturation of growth plates (delayed bone age)
(Cretinism- developmental delay, deafness, severe short stature in babies not screened)
What is the role of glucocorticoid excess in children and how does it present, and the differential diagnoses
Glucocorticoids inhibit growth- excess = Cushings Syndrome
- Increases adiposity, weight and BMI.
- Slowing of growth which may stop
Obese children can look very similar but in childhood they have growth initiated faster, so gaining weight but not growing taller should be considered for endocrine problem:
glucocorticoid excess can look like hypothyroidism, GH deficiency,
What is mid-parental height - how to calculate and what is the height range
Men average 13cm taller than Women
It is an estimate/guide to what the genetic potential of height based on parents
Average the heights of the two parents (M+D)/2 but if child is boy then add 13cm to mum, girl subtract 13cm from dad.
The mid parental height range is +/- 8cm
What is Height velocity, how to measure it and how is it applied
HV= (Difference in height between 2 measurements / time between measurements in months ) x 12.
Growth in centimetres per year
It is calculated over 6-12 month interval to reduce measurement errors,
allowing growth to be tracked over time.
Normal HV lies within the 25-75th centile. Children with delayed or early puberty have different curve