Lecture 20: Postnatal growth Flashcards
What conditions are required for normal somatic growth?
Normal growth depends on:
- Good general health
- A normal hormonal milieu
- Normal genetics
- Adequate nutrition
- Caring environment i.e psychosocial dwarfism
What are the karlberg phases of growth? and what is each stage dependent/independent on/of?
Infant: Rapid growth at birth declining rapidly over the first two years of life - less GH dependent
Childhood: Constant annual growth - GH dependent
Puberty: Rapid growth primarily dependent on sex steroids and increase GH release
Describe the proportion changes during growth:
- Human beings follow a cephalo-caudal gradient of growth
- From birth to puberty the legs grow relatively faster than other post-cranial body segments
Write some notes on growth hormone:
Major anabolic hormone
- Increases muscle mass, bone strength, linear growth in childhood
- Decreases fat mass
Has positive effect on wellbeing.
What can excess GH lead to?
In excess, causes excess growth in childhood (gigantism) or coarsening of features in adults (acromeagly)
Describe growth hormone secretion, what increases and decreases its secretion?
- Pulsatile with low baseline
- Primarily at night
Increased by: Sleep, exercise stress hypoglyceamia, amino acids, malnutrition, sex steroids
Decreased by: Obesity, psychosocial deprivation, excess glucocorticoids
Describe the relationship between nutrition and GH/IGF1 production
- Normal levels of insulin and normal nutrition are essential for normal hepatic IGF-1 production
- Malnutrition or poorly controlled diabetes inhibit hepatic IGF-1 production. (indirect measure of GH, but must be aware of nutrition)
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What are the growth hormones actions:
Metabolic
- Inhibits glucose uptake and promotes glycogenolysis (anti-insulin)
- Stimulates protein synthesis
- Promotes lipolysis
Growth promoting effects
- Endocrine, paracrine and autocrine
Describe GH deficiency:
- Abnormally slow height velocity
- (not being short per se)
- Increased adipocity (truncal)
In babies can have:
- Hypoglyceamia
- Small penis
What are some considerations to make when testing for growth hormone deficiency?
- Random growth hormone levels are not useful
- Best screening test is to look at height velocity
- A normal IGF-1 makes GH deficiency unlikely
- Formal stimulation response test can deduce GH deficiency
What does IGF-1 do? Where does it come from?
- Major post-natal growth promotion (Majority bound to BP-3)
- Principally produced in liver and bone
- Insulin-like (promoting glucose, lipid and amino acid uptake) (cell proliferation and differentiation)
Whats the impact of estrogen on growth:
- Effects on skeleton and body composition
- Estrogen has greater effect on skeleton on than T
- Estrogen is resp. for epiphyseal maturation/closure in both sexes.
- In boys estrogen is responsible for bone maturation (required to fuse growth plate)
Describe how T3 & T4 influences growth:
- Facilitatory role in growth
- Necessary for normal GH secretion
- Necessary for growth plate development (and body proportions)
- Hypothyroidism causes growth failure with delay of maturation of the growth plates (delayed bone age)
What can cause a glucocorticoid excess and what does this cause?
- Glucocorticoid excess causes cushing syndrome (multisystem disorder)
- Exogenous steroids most common
- Endogenous cortisol could be secreted by an adrenal tumor, or stimulated by disordered secretion of ACTH (pituitary adenoma)
Whats the impact of glucocorticoid excess in children:
Major effect on growth and body composition
- Increased adiposity, weight and BMI
- Slowing of growth, which may even stop
- General features of cushing syndrome in adult generally unhelpful in children - Obese children often have abdominal adiposity, roundish face
Obesity drive growth, obese children are taller for their age.
If the child is gaining weight but failing to grow, what should you consider
If the child is gaining weight, but failing to grow should be considered to have an endocrine problem i.e hypothyroidism, glucocorticoid excess, GH deficiency
What are the important hormones of puberty?
Insulin IGF-1 Testosterone GH T3,4 PG E2
How does mid-parental height est. work?
Boys: Dads H + Mums H (+13) / 2
Girls Dads H - 13 + Mums heigh /2
+/- 13
Write some notes on height velocity:
- HV differeniates normal variant stature from pathological short stature
- Calc. over 6-12 months ideally
- HV curve is shaped differently in children with delayed or early puberty
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What is short stature?
- Symptom or a variant
- Variant from normal growth
- May indicate pathology
- Normal short stature grows with normal HV
What is bone age?
- Use of x-ray atlas to use picture matching age of bones
- Enables us to identify delayed (or advanced) bony maturation
- Using the bone age we can predict final adult height
What is normal variant short stature?
- Familial short stature
- Constitutional delay of growth and development
- These 2 diagnoses account for 95% of children who present with short stature
- HALLMARK IS NORMAL HEIGHT VELOCITY (Between 25075th percentiles
