Body growth- effects by the hypothalamus-pituitary.

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Body growth- effects by the hypothalamus-pituitary
.
John-Olov Jansson
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Content

• Body growth general
• Body growth - endocrine regulation
• What are the effects of the GH- IGF-1 axis?
• How is the GH- IGF-1 axis regulated ?
• What are the mechanisms of action
• of GH- IGF-1?
• What can go wrong with GH IGF-1?

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Body growth - general
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Organ growth ( of size at age 20)
LYMPHOID
Size obtain (as adult size)
BRAIN HEAD
GENERAL
REPRODUCTIVE
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Factors that affect growth

1. Genetic
2. Environmental nutrition, illness, stress

• Hormones
• growth hormone,
• insulin-like growth factor 1 and 2, insulin
• thyroid hormones
• Androgens - estrogens,
• glucocorticoids inhibitory.

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Growth in humans

• Growth is not continuous - it is episodic.
• Two periods of physiological rapid growth
• In infancy
• Late in puberty (just before growth stops)In
  addition patophysiological
• (After illness catch-up growth occurs.)

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Growth velocity in boys girls
Growth spurt
Why are men taller?
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Body growth- endocrine regulation
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Endocrine control of postnatal and prenatal
growth
1. Postnatal

• 2. Prenatal (trimester 2 and 3)
• Nutrients (dose response)
• Insulin
• IGF-1
• IGF-2
• Thyroid hormone
• Not GH.

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Induction of growth plate closure by steroids in
men and women
Aromatase
E2 T?E2
Same hormones that cause The growth spurt, but
later!
Females Estradiol acts on ERa in growth
plate. Males Testosterone ? Estradiol acts
on ERa in growth plate.
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Growth hormone

• Endogenous produced by
• anterior pituitary GH-N, GH gene (somatotrophs)
  pulsatile
• placenta - GH variant continuous, 3rd
  trimester, secretion to mother. not fetus, may
  increase B-glucose in mother ? more nutrients for
  fetus?.

(In addition 3 placental lactogen genes)
GH-V (pla- centa)
GH-N (pit)

• GH therapy
• Human GH protein (192 amino acids, 4 ?-helices)
  must be injected.
• Without GH proportional dwarf 110 cm.
• GH tumour Giant if not adult. 270 cm. ? Wide
  dose response! (maybe also for IGF-1.)

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Body growth- Effects by the GH - IGF-1 axis
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What does GH do? One opinion
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What does GH do?
Where is Belitze located?
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Belize (former British Honduras) Where Dr
Klatz got his MD
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GH is anabolic, lipolytic and diabetogenic
GH
? Lean body mass
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GH therapy reduces visceral adiposity in
GH-deficiency Influence on risk cardiovascular
diseases?
GH-deficient patient before GH therapy
GH-deficient patient after 26 weeks GH therapy
Bengtsson et al 1993 J. Clin. Endocrinol. Metab.
76309
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Body growth Regulation of GH - IGF-1 axis
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Physiological control of GH secretion
Stress
Exercise
Fasting
Sleep




_
GH
Aging
Gonadal steroids


_
_
_
GH/IGF-1
Arginine
Glucose
Lipids
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Control of GH secretion
Hypothalamus
somatostatin
GHRH
_
Portal vessels
Anterior pituitary
Growth Hormone
Liver
IGF-1
Insulin-like growth factor-1
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Nutrient control of GH secretion in relation to
GH effects
GH
_
_


Amino acids (Arginine)

_
Lipids (FFA)
Glucose
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Implications of pulsatile GH secretion

• Single GH blood samples
• not good enough
• How to destinguish?
• 24 h GH pattern (golden standard)
• Serum IGF-1 as marker
• of mean 24 h GH
• Stimulators or inhibitors

GH levels
GH prod tumor
X
Normal GH pattern
X
GH deficiency
X
Time
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Effect of arginine on plasma GH
hGH µg/ml
100
Arginine can be used as a provocactive test for
GH release
80
60
40
Normal
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GH deficient
Arg
0
-10
0
30
60
90
120
Time (minutes)
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Glucose tolerance test
Acromegaly (nonresponsive to glucose)
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GH mU/ml
6
Normal
3
0
0
4
2
Hours
Glucose
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GH secretion is increased by gonadal steroids
during growth spurt, then declines
Age 7 years
Age 13 years (Due to E2 in girls, due to T ? E2
in boys)
Serum GH (mU/L)
Age 20 years
Age 30 years
CLOCK TIME
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GH secretion during sleep
Clock time
STAGE
SWS
Plasma GH ?g/l
SWS slow wave sleep
Clock time
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Fasting increases GH secretion in man

• Effects
• Keep B-glucose up
• Lipolysis
• Does NOT increase growth

Bergendahl et al, 1999
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GH, IGF-1 and fasting
? B-glucose

• IGF-1 stimulated by GH and Nutrition (partly via
  insulin).

? Lipolysis
? GH
FASTING
? ? Body growth
Fasting blocks GH effects on body growth and
IGF-1 ? Appropriate response to fasting
? IGF-1
Needed for IGF-1 synthesis GH and food!
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Somatotrophs GHRH and somatostatin Regulates GH
synthesis release cell replication
Somatostatin
GHRH
AC

G-prot
-
cAMP
PKA
CREB
Pituitary somatotroph
CREB
P
1 GH synthesis
GH
3 Proliferation
GH
Taken from PhD thesis of Tanya Gilbert, MRC
NIMR, London
2 GH Secretion
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Ghrelin pharmacologic regulator of GH

• A peptide fatty acid hybride (see below)
• Ghrelin treatement stimulates GH release.
• Ghrelin knockout mice lean but not small!
• Released from the empty stomach between meals
• Increases appetite
• Increases fat mass
• Decreases fat burning (increased RQ)

Ghrelin receptors In GHRH (growth) And NPY
(body fat) neurons in arcuate nucleus (ARC)
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Ghrelin a centrally active hormone from the
empty stomach
Hypothalamus
? Growth hormone
? Fat mass ? Food intake
Pituitary
Stomach (oxyntic glands)
Ghrelin

-
Negative Energy Balance
Positive Energy Balance
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Possible mechanism for adiposity Ghrelin gt ? RQ
(? Fat/CHO burning)
Respiratory quotient (RQ)
Tschöp et al, 2000, Nature 407908
Lall et al, 2001, BBRC 280132-138)
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Body growth- Mechanisms GH IGF-1 axis
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Growth of long bones before epiphyseal plate
closure
Epiphyseal plate
Geminal
Proliferative
Chondrocytes
Hypertrophic
Calcifying
Oestrogens induce closure of the growth plate
via ERa.
Endochondral growth
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Somatomedin (IGF-1) hypothesis of GH action on
bone
Salmon Daughaday, 1957

• GH actions to stimulate bone growth are mediated
  by insulin-like growth factor 1 (IGF-1), produced
  by the liver.
• IGF-1 - previously called somatomedin C.

GH
IGF-1
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Challenge to the somatomedin hypothesis - I
Experiment Administration of GH to growth
plate of one leg.
GH
NaCl
GH acts locally within the epiphyseal plate to
promote growth. No effect via liver IGF-1 on
Contralateral leg
Direct action of GH? Locally produced IGF-1 needed
Olle Isakssson and coworkers, Science 1982
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Challenge to the somatomedin hypothesis - II

• Additional Experiment IGF-1 antiserum (removes
  IGF-1) GH to growth plate of one leg.
• Result No increase in growth of injected leg.
• Conclusion GH actions require the presence of
  IGF-1.
• IGF-1 may be produced locally.

GH plus IGF antiserum
NaCl
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Challenge to the somatomedin hypothesis - II
Liver IGF-1 knockout
Normal body growth in liver-specific
IGF-1-knockout mice. ? Liver-derived IGF-1 may
not be important for growth.
Control
24
20
Body Weight (g)
16
12
8
0
0
10
20
30
40
50
Days after induction of knockout
Sjögren K, Ohlsson C et al, PNAS 1999
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Modified somatomedin (IGF-1) hypothesis
Green et al, 1985
The local actions of GH within the growth plate
require the presence of IGF-1

• Needed for growth
• Direct GH effect.and
• IGF-1 (liver or
• local)
• IGF-1 can not
• replace GH if GHD.
• GH no effect in
• IGF-1 knockout mice

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Revised GH action on bone

• GH actions to stimulate bone growth are direct on
  the bone.
• The effects are partly mediated by local IGF-1.

GH
GH
IGF-1
IGF-1
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GH receptor dimerization for biological effect
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GH Receptor signaling Active STAT dimer to
nucleus
GH
2
1
GH receptor
JAK2
Nucleus
Nucleus
STAT5b
Phosphotyrosine Binding domain
STAT signal transducer and activator of
transcription
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Serum IGF-1 levels determine sizes of dog breeds
IGF-I
IGF-I
IGF-I
Polymorphism near IGF-I gene associated with
body size of dog breeds
IGF-I
IGF-I
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Comparisons between IGF-1, IGF-2, and insulin
The ligands bind mainly to their own receptors ,
but also to others with lower affinity
Insulin- and IGF-I Receptors ? Biological
signaling IGF-II Receptors ? Scavenging of
ligand.
Scavenger receptor?
Derek LeRoith NEJM 1997
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The insulin-like growth factor (IGF) system
IGFBP-3 ALS binds most of all IGF-1 in serum.
IGF-IIR
IGF-IR
Insulin-R
Courtesy of Dr Ricarda Granata
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Interactions between IGF-1, IGF-BP3, ALS and BP3
protease
BP3 Protease (Prostate Specific Antigen PSA)
ALS acid labile subunit (old term)
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Beware of IGF-1? 1) tumors

• IGF-1 stimulated proliferation
• IGF-1 inhibits apoptosis.
• In epidemiologic studies High S-IGF-1 predictor
  of breast cancer, prostate cancer, colon cancer
• Low S-IGF-BP3 predictor of cancer.
• PSA (IGF BP3 protease) a clinical marker of
  prostate cancer

IGF-1 is still approved by FDA for the
indication Low growth in children, irrespective
of cause. Caution!
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Beware of IGF-1? 2) longevity.
? Longivity
2/3 ? food intake
?GH effect ? S-IGF-1 insulin
Genetic growth defects
?

• Animals with ? IGF-1 that all live longer
  (15-30!)
• Semi-starved animals, 2) Growth mutants (GHRH-/-
  (Little) mice, ames
• dwarf mice, GHR-/-, IGF-1/- etc.)

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Body growth- GH - IGF-1 axis pathology
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Gigantism
Excessive GH production in childhood, or before
the epiphyseal growth plates have fused
Dose-response 110-270 cm!

• Cause
• Pituitary tumour that start from a somatotrophic
  cell.

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Acromegaly
Excessive GH production in adulthood after the
epiphyseal growth plates have fused. Growth of
the tips of the body.

• Cause
• Pituitary tumor that starts from a somatotrophic
  cell.

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Clinical features of acromegaly
Large nose Thick lips Growth of
mandible Prominent cheek bones
Visual field defects (bitemporal hemianopia)
Hirsutism
Barrel chest
Osteoarthritic vertabral changes
Often caused by Lack of GTPase activity in
G-protein (see next slide)
Enlarged hand feet
Excessive sweating
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Molecular cause of acromegaly in a somatotroph
40 of acromegaly in Europeans.
GTPase
Arg201 in G-protein changed ? No
dephosphorylisation by GTPase ? No signal
termination ? 1 GH prod, 2 GH release, 3
Somatotroph proliferation
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Kända genetiska defekter med proportionerliga
tillväxtrubbningar

• Pit-1 defekt. Snell (dw/dw) Anläggning GH, TSH,
  PRL celler. Prop-1 Prophet of Pit defekt.
  Ames (df/df) GH, TSH, PRL LH FSH Dvärgmöss,
  Master genes. Människor också. ? Livslängd??
• GHRH receptor gen little mus. Människor Bangla
  Desh, Sydamerika.
• GH gen. Antikroppar mot GH!
• GH receptor gen. Laron dvärgar. IGF-1 behandlig
  delvis effektiv.
• STAT5b gen. IGF-1 behandlig delvis effektiv.
• IGF-1 gen. Mental retardation, hörselpåverkan.
  IGF-1 behandling.
• IGF-1 receptor gen. Som IGF-1 defekt. Ej effekt
  av IGF-1.
• (Fibroblast growth factor-receptor 3 (FGFR3) gen.
  Achondroplasi, korta armar och ben, alltså EJ
  proportionerlig.)

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Monogenetic causes of dwarfism Defective GH axis
Ghrelin-R Mutation?
Ghrelin-R
somatostatin
GHRH
Defective development of somatotrophs
GHRH-R Mutation
Little Dwarfism
GHRH-R
Defective GH gene
GH-R Mutation
Laron Dwarfism
GH
GH-R
IGF1-R mutations
? IGF-1 synthesis release
Target organs
IGF-1
IGF1-R
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Dwarf mice and human equivalents defective
pituitary master genes
GH
Pit-1 1. Mediator of GHRH effect on GH
production postnatally 2. Inducer of pituitary
development prenatally Defect earlier in
development, (e g Prop-1 instead of Pit-1) ? More
hormones lacking.
PRL
Stem cell
Stem cell
TSH
LH, FSH
Prop-1 Defect Ames Dwarf mice Human dwarfs
(Krk)
Pit-1 Defect Snell Dwarf mice Human dwarfs
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Evidence that the GHRH-receptor, and not
down-stream pathways, is nonfunctional in dwarf
little mice
GH secretion from pituitaries of Little mice is
decreased after GHRH compared to Wild type
mice. In contrast, stimulation of the down stream
G-protein adenylate cyclase (AC) cAMP signal
pathway by cholera toxin, forskolin or dbcAMP
can all stimulate GH secretion in little mice
(Adapted from Jansson et al Science 1986)
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Dwarfism due to mutations of human GHRH receptor
Brazil (intron 1 splice donor)
Gly
Asp
NH
2
Little mouse
Effect of Sindh Mutation (Ala?Glu)
T
A
Sindh
E
Stop
Glu
C
I
Y
C
S
V
L
F
V
S
V
I
T
G
W
S
H
A
A
H
G
V
T
T
G
R
V
V
L
T
A
S
I
S
F
A
K
L
F
G
L
N
F
T
S
M
T
F
I
L
A
V
I
P
D

4
S
F
A
V
W
G
A
T
F
L
W
L
L
W
L
V
T
H
Q
L
A
E
A
L
T
I
I
Japan
A
F
A
W
L
V
N
Y
Y
L
V
V
L
Leu
His
P
Ala
Glu
Cys
Spain
Phe
Pakistan
USA
USA
COOH
C
M
S
L
K
A
W
K
W
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GH receptor deficiency (Laron dwarfism)
X
X

• GH treatment ineffective
• IGF-1 only small effect
• (lack of cells with IGF-1 rec
• in growth plate when no GH?)

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IGF-1 and IGF-1 receptor deficiency
IGF-1 receptor gene defect
IGF-1 gene defect
Intrauterine growth defect
Intrauterine growth defect
Chernausek S et al NEJM 2003
Chernausek S et al NEJM 2003
Woods KA et al NEJM 1996
Woods KA et al NEJM 1996
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Causes of dwarfism unrelated to GH-IGF axis

• Thyroid hormone deficiency in childhood
  (Cretinism).
• Retardation of mental development growth.
• Thyroid hormones are permissive for growth.
• Excess glucocorticoids - stunts growth.
• Glucocorticoids are permissive for growth, but
  inhibitory in high doses.
• Genetic diseases
• Pygmy mouse, HMGA2 (high-mobility group A2), a
  transcription factor for e g cycline A.
• Human SNP 0.5 cm height.
• Achondroplasia (next slide)

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Achondroplasia Selective shortening of long
bones in dogs and humans.
Diego Velázquez (1599-1660). Museo del Prado,
Madrid
Not responsive to GH or IGF-1 treatment.
Hypothesis Gain of function mutation in
fibroblast growth factor receptor-3 (FGFR-3).
FGFR3 prevents stem cell proliferation and
differentiation. (Autosomal dominant disease.
Logical.)
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Transmembrane mutation G380A causes
over-activation of FGFR3

• 1. Constitutive dimerisa-
• tion and activation of
• 50 of FGFR3.
• (Stronger signal.)
• 2. Less degradation by
• lysosomes
• Inhibition of stemcell
• proliferation and
• differentiation

(Horton WA 2006, Growth Genetics Hormones. Vol
4)
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Summary

• Prenatal, postnatal and pubertal body growth is
  regulated by different hormons.
• Postnatal longitudinal body growth is regulated
  by a hypothalamus pituitary liver bone
  axis.
• GH is dibetogenic and lipolytic in addition to
  growth promoting.
• GH- IGF-1 is axis regulated by feeding, amino
  acids, lipids and glucose.
• GH- IGF-1 in relation to tumor growth is a
  concern, but few alarming data at present.
• Dwarfism can be due to defects of various
  hormones and receptors in the GHRH - GH- IGF-1
  FGFR3 axis. Diagnos for right treatment.

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Effects of GH and IGF-1 on different nutrients
TÄNK IGENOM! BRA ATT HA MED?? FÖRE FASTEBILDEN?
? Growth/Protein anabolism ?
_
GH
? B-glucose ?
IGF-1


? Lipolysis ?

Nutrition

• GH and IGF-1 both stimulate growth, but have
  different effects on fat and sugar.

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Elevated GH following ectopic GHRH secretion
Plasma GH and GHRH in acromegaly
GH
40
30
ng/ml
20
10
GHRH
10.00
14.00
18.00
22.00
02.00
06.00
Hours
Vance et al, 1985
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Ghrelin treatment elevates pulsatile GH
secretion in the elderly
However Uncertain if endogenous ghrelin is
important for GH secretion in humans. (Not
important in mice. Ghrelin KO mice normal
growth.)
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Molecular cause of acromegaly

• Arg201 in G-protein changed ?
• GTP hydrolysis activitity disrupted. ?
• No signal termination ?
• G-protein-alpha-GTP and adenylate
• cyclase (AC) remains active. ? cAMP ?
• Somatotroph growth
• GH prod
• GH release.
• Cause of 40 of acromegaly
• in Europeans.
• (Cholera Toxin ADP-ribosylates Arg201?
• ? GTPase activity in gut diarrhoea.)

(GTPase)
Active AC cAMP
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Courtesy of Dr Kelly Mayo Northwestern University
Chicago
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GH Receptor signaling II
STAT3 with phosphotyrosines forms dimer and
goes to the nucleus