BIOL 1080 Lecture Notes - Lecture 7: Pituitary Gland, Insulin-Like Growth Factor 1, Skeletal Muscle
2 May 2018
School
Department
Course
Professor
Growth and development
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Homeostasis
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Reproduction
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Many other things in CCN (e.g.
neurodevelopment and immunity)
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Role of Hormones… modulation of:
Endocrine glands, nerves
1.
Target organc that produce hormones as a
secondary function
2.
Hormones come from…
*what's missing? --> adipose and skeletal muscle
Some nerves release their neurotransmitters
directly into the bloodstream (neurohormones)
1.
E.g. norepinephrine: increase epinephrine,
decrease insulin
○
All primary endocrine glands and secondary
endocrine tissue are innervated by neurons of the
autonomic nervous system
2.
Neurons in the CNS and PNS have receptors for
many hormones (e.g. insulin, estrogen and
testosterone)
3.
The nervous system interacts with the endocrine system
to form the foundation of the CCN:
Anterior pituitary acts like a gland -contains
endocrine cells that release many hormones
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*see slide
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Hypothalamus releases GHRH (sex
hormones, deep sleep) --> Anterior
Pituitary Gland
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GH acts on liver (stimulates release of
IGF-1 --> anabolic effects), bone, muscle,
adipose (promotes lipolysis)
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Muscle actually not so much, except
when administered in cases of
deficiency
!
*note: skull and facial bones can still grow
under influence of GH in adulthood
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Lots of "popular press" regarding
supplements that naturally enhance GH
(arginine, melatonin)
○
5mg of melatonin (orally) increased
GH release after exercise
!
Interestingly, the exercise was 8
minutes of cycling at 70% VO2 max
(evidence is referred to on body
building web sites)
!
Clinical Study: exercise-induced GH
secretion is enhanced by the oral ingestion
of melatonin in healthy adult male subjects
○
Melatonin (0.5-5.0mg)
increased GH response to
exercise only in males
□
The investigators did not
control for menstrual cycle in
females
□
Results:
!
Study: effects of a single dose of N-
Acetyl-5-methoxytryptamine (melatonin)
and resistance exercise on the growth
hormone/IGF-1 axis in young males and
females
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Subjects were 8 young males
!
Arginine dosage was 7g
!
Over 10g starts to cause nausea and
diarrhea
!
Protocol was 10 different exercises,
3 sets each @ 80% of 1 RM
!
Result: exercise alone is the best!
!
Study: oral arginine attenuates the growth
hormone response to resistance exercise
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Growth hormone:
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Hormones of the Anterior Pituitary:
Young males
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Curls alone
!
Or followed by leg presses and
extensions to markedly increase GH,
testosterone and IGF
!
Perform biceps curls for 15 weeks under 2
conditions:
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Study design:
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Bottom line: increases in biceps size and strength
are the same in both conditions
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Resistance exercise training with or
without GH administration increases FFM
and muscle size/strength
○
The combination of resistance training and
GH administration is no more effective in
increasing muscle size and strength and the
rate of muscle protein synthesis than
resistance training without GH
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After 12 weeks of training:
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Dogma: heavy exercise with large muscle groups
increase GH and testosterone which will promote
overall muscle hypertrophy
Bind to androgen receptors, but some can bind to
estrogen receptors
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Differential metabolism in tissues (e.g. converted
to DHT in testes, converted to estrogen in
muscle, AT)
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Some have both myogenic (protein synthesis)
and androgenic (masculinizing) effects
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As with testosterone, can affect cognitive
function and behaviour/arousal (roid rage)
•
Effective dose is supraphysiological
○
Hormones are released according to
complex ultraradian, circadian and
infradian rhythms
!
Dose of the hormone/hormone agonist is
generally not timed to mimic natural
hormone production
○
Reasons why anabolic steroids can be harmful:
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Steroid Metabolism -variable and hard to predict
Anterior pituitary releases many more
hormones
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Note: posterior pituitary releases
neurohormones made in the hypothalamus
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Main point: posterior pituitary releases oxytocin
and antidiuretic hormone
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Oxytocin -uterine contraction, milk
ejection, positive mood
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ADH -retention of fluid by kidneys
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Posterior pituitary isn't really a gland, more like a
collection of nerve endings that release oxytocin
and ADH into the pituitary's circulation
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Hormones of the Posterior Pituitary:
Endocrine System
Monday,*October*23,*2017
12:14*PM
