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RC Peds Endo 2023 > Growth > Flashcards

Growth Flashcards

1
Q

CDC v WHO growth curve

A

WHO
- Breastfed infants to 12m
- How kids should grow in ideal conditions
- No weight plot after age 10yrs – recommend plotting BMI only
- Addition of %iles – up to 99.9th and down to the 0.1th %iles
- International sample population (vs.US)

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2
Q

GH receptor action

A
  1. Dimerization of GH receptors
    i. Different domains of a single GH molecule associate with homologous regions on 2 independent GH receptors, promoting dimerization of the receptors.
    GH receptor lack a tyrosine kinase domain
  2. Recruitment of JAK2 (Janus Kinase 2)
    i. With dimerization, JAK2 is associated with and activated by the GH receptors.
  3. Activation of JAK2’s intrinsic tyrosine kinase activity
    i. JAK2 undergoes autophosphorylation and concurrently tyrosine phosphorylates the GH receptors
  4. Recruitment of STAT (Signal Transducer & Activator of Transcription) Factors:
    i. The phosphorylation of the GH receptors by JAK2, provides a docking station for STAT factors (STAT5a & STAT5b are most relevant to GH).
  5. Transcription
    i. STATs are phosphorylated. They dissociate from the GHR, migrate to the nucleus, and bind to specific STAT-binding DNA regulatory elements (SIE/ISRE/ GAS) responsible for transcriptional control of GH target genes such as IGF-1.
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3
Q

How to measure proportions

A

1) U/L segment ratio
- lower segment = from the pubic symphysis to the ground while the child is standing straight with shoes off and feet
together
- upper segment= Subtract the lower segment from the total height
- Calculate ratio
**Normal is 1.7 in neonate to slightly below 1.0 in the adult.

2) Arm span
- Measure child’s arm span while she/he is standing with back touching wall and feet together. Arms should be fully extended against the wall and parallel to the floor with fingers together and outstretched, palms facing forward. Measure straight across (to length of 3rd finger), on the wall, once the child has stepped away.
**Should be ~ equal to height

3) Head circumference
- Measure from the occiput to the forehead around the head – objective is to measure maximal HC. Rpt 3x.
- Plot measurement on growth curve

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4
Q

causes of disproportionate grwth

A

Increased U/L
1. Achondroplasia
2. Hypochondroplasia
3. Turner
● Osteogenesis imperfecta
● Hypophosphatemic rickets
● (Pseudo)pseudohypoparathyroidism

Decreased U/L
1. Scoliosis

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5
Q

where is the Main organ GH acts to make IGF1

A

liver

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6
Q

GH R- what does it activate and cause

A

activates post receptor signaling through JAK/STAT

Leads to transcription of 3 important GH dependent genes:
IGF-1
IGFBP-3
ALS (acid labile subunit)

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7
Q

Pharmacologic agents that stimulate secretion of GH

A
  • AMINO ACID
    Arginine
  • NEUROTRANSMITTER
    Clonidine (alpha adrenergic agonist)
    L-dopa (dopamine agonist)
    Propranolol (beta-adrenergic antagonist)
    GABA agonists (muscimol)

ALPHA AGONIST
BETA ANTAGONIST

  • HYPOGLYCEMIA
    Glucagon (relative hypoglycemia)
    Insulin (hypoglycemia)
  • HORMONES
    GHRH
    Peptide–ACTH, alpha-MSH, vasopressin
    Estrogen
  • OTHER
    Potassium infusion
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8
Q

Physiologic agents that stimulate secretion of GH

A

Hypoglycemia
Exercise
Sleep
Stress
Protein depletion/starvation/AN
Chronic renal failure
Ectopic production of GHRH
Acromegaly (TRH, GnRH)

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9
Q

physiologic inhibitors of GH secretion

A

Hyperglycemia (postprandial)
Elevated FFA
Obesity
Hypo or hyperthyroidism
Somatostatin
Progesterone
Glucocorticoids
Alpha adrenergic inhibition
Beta adrenergic stimulation (GH)

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10
Q

hormones involved in growth

A

GH
TH
Sex steroids
GC

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11
Q

Growth hormone - other name
- stimulated by
- inhibited by

A

somatotropin

stimulated by GH-releasing hormone (GHRH or GRF)

suppressed by hypothalamic GH release-inhibiting factor (somatostatin or SRIF)

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12
Q

Clinical signs of GHD

A
  • Poor growth
    (increased fat mass leading to a chubby or cherubic appearance with immature facial appearance, immature high-pitched voice, and delay in skeletal maturation)
    midface hypoplasia
  • Neonatal Hypoglycemia
  • Prolonged jaundice
  • Micropenis
  • breech position
  • delayed dentition
  • giant cell hepatitis
  • midline defects
  • higher incidence of hyperlipidemia with elevated total cholesterol and low-density lipoprotein
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13
Q

meds to use in GH stim

A

L-Dopa
Clonidine
Arginine
Glucagon
Insulin-induced hypoglycemia (very dangerous)
GHRH
Growth hormone–releasing peptides (GRP)

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14
Q

achondroplasia
gene

features

A

FGFR3 mutation

frontal bossing
mid-face hypoplasia
exaggerated lumbar lordosis
limited elbow extension
genu varum
trident hand
motor delay
spinal stenosis
obesity

intelligence normal

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15
Q

Russell silver syndrome

criteria for dx

A

4/6 of:
3 growth, 2 head, 1 body

  1. SGA (birth weight and/or length ≥2 SD below the mean for gestational age)
  2. Postnatal growth failure (length/height ≥ 2 SD below the mean at 24 months)
  3. Relative macrocephaly at birth (HC >1.5 SD above birth weight and/or length)
  4. Frontal bossing or prominent forehead (forehead projecting beyond the facial plane on a side view as a toddler [1–3 years])
  5. Body asymmetry (limb length discrepancy ≥0.5 cm, or <0.5 cm with ≥2 other asymmetric body parts)
  6. Feeding difficulties or body mass index ≤2 SD at 24 months or current use of a feeding tube or cyproheptadine for appetite stimulation
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16
Q

What does SHOX stand for

A

Short stature HOmeoboX-containing gene

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17
Q

Noonan syndrome features

A

short stature,
webbed neck,
low posterior hairline,
facial resemblance to Turner syndrome

the karyotype is 46,XX in the female or 46,XY in the male

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18
Q

PWS features

A

poor intrauterine movement,
acromicria (small hands and feet),
developmental delay
almond-shaped eyes along
infantile hypotonia
poor feeding as infant

short stature
insatiable hunger
obesity
glucose intolerance
delayed puberty

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19
Q

PWS gene

A

lack of expression of paternally inherited imprinted genes on chromosome 15q11-13

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20
Q

when to stop GH therapy

A

GV <2cm/y
BA fused

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21
Q

GH tx s/e

A
  • intracranial hypertension
  • SCFE
  • scoliosis progression
  • Insulin resistance
  • edema
  • Theoretical increased risk of malignancy
  • Gynecomastia (for boys)
  • Carpal tunnel syndrome
  • Local reaction at site of injection
  • Increased growth of nevi (?)
  • Hypertrophy of tonsils/adenoids (?)
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22
Q

Laron syndrome

A

= GH insensitivity

Molecular mechanism:
- Primary GH resistance - Receptor mutation (decreased or absent).
Note: Decreased serum GHBP levels
- GH insensitivity - Post-receptor defects.
Note: Normal GHBP levels
- Primary IGF-1 deficiency – synthesis or receptor

Autosomal recessive
GH elevated due to decreased or absent IGF-1
Does not respond to GH treatment… need recombinant IGF-1

23
Q

nonendo causes tall

A
  • constitutional tall stature
  • genetic tall stature
  • syndromes of tall stature
    —Klinefelter
    —Marfan
    —-Cerebral gigantism
    —Homocystinura
    —Beckwith-Wiedemann
    —XYY and XYYY syndromes
24
Q

endo causes of tall stature

A

Pituitary gigantism
Sexual precocity
Thyrotoxicosis
IDM

25
Q

name of GH excess

A

pituitary gigantism before epiphyseal fusion
acromegaly after

26
Q

features of pituitary gigantism

A

Grow excessively rapidly,
coarse features,
large hands and feet with thick fingers and toes, and
often frontal bossing and large jaws

glucose intolerance or frank diabetes mellitus,
hypogonadism, and
thyromegaly

27
Q

causes of pituitary gigantism

A
  1. GH secreting pituitary adenoma or somatotrophs
  2. constitutive activation of GH secretion as is sometimes found in the McCune-Albright syndrome
  3. excess secretion of GHRH
  4. ectopic GH secretion (rare)
28
Q

test for GH xs

A

GH suppression test with OGTT
1.75g/kg oral glucose (max 75g)
measure serum GH before and two hours after glucose administration
GH should be <1 or 5 ng/L depending on resource

29
Q

when do igf1 peak

A

1 year after peak growth velocity is reached and remain elevated for 4 years thereafter, even though growth rate is decreasing

30
Q

IGFBP3 levels proportional to?

A

Levels directly proportional to GH concentration and nutritional status

31
Q

wha regulates IGFBP3 synthesis?

A

GH, testosterone, estrogen, and thyroxine

32
Q

Adv of measuring IGFBP3

A
  • Not pulsatile, thus measured level reflective of serum levels
  • IGFBP-3 is the major serum carrier protein for IGF-1 and the most GH-dependent
  • Less nutritionally dependent than GH
  • More discriminatory than those of IGF-1 in the lower end of the normal range
  • IGFBP-3 is a better screening test for GHD than IGF-1 in younger children because it is easier to distinguish low-normal levels of IGFBP-3 in young children from truly low levels
33
Q

FGFR3 mutation causes what?

A

inability to form bone from cartilage

34
Q

factors that affect IGF1 levels

A
  • Age (lower in infants, increases during childhood and peaks around puberty)
  • Pubertal status (levels are higher)
    ○ During adolescence, levels correlate with Tanner stage or BA vs. chronologic age)
    ○ Sex steroids stimulate IGF-1 production
  • Malnutrition
  • GH deficiency (levels are lower)
  • GH resistance (levels are lower)
  • IGFBPs
    ○ Influence virtually all assays
    ○ IGFBP3 directly proportionate to GH concentrations, but also to nutritional status
  • Liver disease (levels are lower)
    ○ (liver is major site of IGF-1 synthesis)
  • Renal disease (can have normal levels but reduced activity)
  • Thyroid disease (ie: levels are lower in hypothyroidism)
  • Illness – acute or chronic
  • Uncontrolled diabetes mellitus (levels are lower)
  • GH receptor defects
    GH receptor antibodies
35
Q

Benefits of treating adults w GH

A

improvement in:
- body composition (decrease in total body fat & increase lean body mass with GH administration)
- exercise capacity
- dyslipidemia
- improved CV outcomes
- QOL

*tends to increase insulin resistance

36
Q

how to test adults for GHD

A

> one month off GH
IGF1

dn’t need to test if:
3+ pit hormone deficiencies OR
GHD plus structural pituitary of hypothalamic defect or causal genetic mutation

37
Q

FGFR3 mutation

A

achondroplasia
hypochondroplasia

38
Q

syndromes w SHOX mutation

A

Turner Syndrome
Leri-Weill dyschondrosteosis (heterozygous defect - haploinsufficifency)
Langer mesomelic dysplasia (homozygous defect)

39
Q

Syndromes with XS GH

A

MAS
MEN1
Carney Complex

40
Q

Marfanoid syndromes

A
  • Marfan syndrome
  • Homocysteinuria
  • MEN2B
  • Loey Dietz
41
Q

cells that make GH

A

Somatotrophs

42
Q

inhibitors of GH secretion

A
  • Hormones
    ○ SRIF
    § Inhibits release, not synthesis
    ○ IGF-1
    ○ Hypothyroidism
    § TH is important for GH release
    ○ Glucocorticoids XS
    § Deficiency - can be inhibitory
    § Chronic admin
    ○ Leptin
    ○ GH deficiency
  • Nutrition
    ○ Glucose / hyperBG
    ○ FFA
    ○ Malnutrition
    ○ Chronic disease
  • Liver disease
  • Hypothyroidism
  • Uncontrolled DM
  • Other:
    ○ Depression
    ○ Emotional deprivation
    ○ β-adrenergy
    ○ Chronic stress
    ○ Older age
    ○ Obesity
43
Q

stimulators of GH release

A
  • Hormones
    ○ GHRH
    ○ Ghrelin
    ○ Thyroid hormone
    § Important for release
    ○ Estrogen
    § Inhibits IGF1 which increases GH secretion
    § Also increases GH reponsiveness
    ○ Testo
    § Increases centrally
    § Also increases GH reponsiveness
    ○ Dopamine
    ○ Glucocorticoids
    § Acute
    □ Can be used as a stim test
    ○ Glucagon
    § Mech unclear, likely from rebound hypoBG
    ○ Insulin
  • Hypoglycemia
  • Nutrition
    ○ Fasting
    ○ Protein/amino acids
    § Arginine
    ○ Malnourished
    ○ Low FFA
  • Other:
    ○ Younger age
    ○ Puberty
    ○ Sleep
    ○ Galanin
    ○ Alpha agonists
    § Clonidine
    § Prob increased GHRH
    ○ Beta antagonists (beta adrenergy inhibits GH)
    § Propranolol
    § Through somatostatin
    ○ Exercise
    ○ Stress
    ○ Trauma
    ○ Sepsis
44
Q

is GH catabolic or anabolic

A

anabolic

45
Q

3 major physiologic (hormonal) regulators of growth hormone secretion

A

a. Growth hormone releasing hormone (GHRH)
b. Somatostatin
c. Ghrelin

46
Q

Other than growth, three major physiologic (metabolic) effects of growth hormone in the body

A

a. Increased lipolysis and lipid oxidation, which leads to mobilization of stored triglyceride
b. Stimulation of protein synthesis
c. Antagonism of insulin action which may lead to glucose intolerance and diabetes
d. Phosphate, water, and sodium retention

47
Q

indications that the patient will need GH in the long term

A
  • If patient has known genetic mutation causing GH deficiency
  • If patient has >/= 3 pituitary hormone deficiencies
  • If patient has structural brain anomaly to explain GH deficiency (except ectopic posterior pituitary)
  • Pituitary tumor
  • Infiltrative disease
  • hypoglycemias
48
Q

def ISS

A

SD < /= -2.25
predicted adult hight is unlikely in normal range

49
Q

def SGA w no catch up

A

Birth W and L </= -2.25
Lack of catchup in first 2 years

other causes ruled out!!

50
Q

false low in GH - causes

A

obesity
prepubertal not primed
hypothyroid
not fasting
error in dosing

51
Q

investigations to investigate comorbidities associated with acromegaly

A

Cardiomegaly - ECHO
HTN - BP Measurement
Visual field defects - Ophthalmology exam
Sleep apnea - Sleep study
Osteoporosis - Lateral spine x-ray

52
Q

complications of GH excess

A

osteoarthritis, OSA, carpal tunnel syndrome, CVD, diabetes mellitus, HTN

53
Q

Tx GH excess

A

dopamine agonist

somatostatin agonist

GHreceptor blocker (pegvisomant)

RC Peds Endo 2023 (17 decks)

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