Flashcards in ME04 - Anterior Pituitary Deck (56)
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1
If the infundibulum is transsected what happens?
If transsected, there will be temporary cessation >> neurons then regenerate but with malfunctions (more or less)
2
Feedback Control of AP Hormone Secretion
Stimuli >> Hypothalamus >> Anterior Pituitary >> Target Organ >> Tissues
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Causes growth of all or most body tissues
Promotes differentiation of specific cell types (e.g., bone growth cells)
Single chain; 191 AA residues _
Growth Hormone (Somatotropin)
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Prequisite of Growth Hormone
Sufficient insulin activity & CHO
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Growth Hormone is stimulated by:
Mitosis
Cell size
Cell number
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Type of secretion of GH
Pulsatile secretion
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Why is GH Relatively low during the day?
_s during first 2 hours of deep sleep
Regular nocturnal peak: 1 hour after Stage 3 or 4 deep
sleep onset
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GROWTH HORMONE INFO:
Preceded by nocturnal plasma GHRH peak
Biologicalt1_2=20mins
- Serum GH level varies widely
- GH secretion in women > men (highest before ovulation)
- Rate: highest in late puberty, neonate; lowest in older/obese adults, hypothyroidism, Type 2 DM
- Average plasma concentration - 5-20 years old: 6 ng/ml
- 20-40 years old: 3 ng/ml
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Lifetime Pattern of GH Secretion
40-70 years old: 1.6 ng/mL
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Stabilization of 24-hour pulsatile GH secretion rates (200-600 _g/day)
Approximate those in post-pubertal young adults
Pre-puberty GH secretion
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Growth Hormone in Puberty
1.5-3-fold_pulsatileGHsecretion
- With proportionate _ in plasma insulin-like growth fac- tor-I (IGF-I)
- Physiological GH hypersecretion driven by onset of _ sex-steroid hormones
- Correlatewithrateof_inheight
- GHRH response: tall adults > ave height
- Final height (FH) may partly be determined by inherent GH secretory capacity
- In normal children with idiopathic short stature - GH treatment significantly _ FH in a dose-dependent man- ner
- Mean gain = 1.3 SDS (8 cm) and a broad range of re- sponse from no gain to 3 SDS compared to a mean gain of 0.2 SDS in the untreated controls. (Al- bertsson-Wikland, 2008)+A12
12
Growth Hormone in adulthood
Starting 18-25 y/o GH secretion _s up to pre-pubertal level (
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Growth Hormone in Aging
_ GH secretion - Correlated to
- _ total body & visceral fat %
- Muscle wasting
- _ physical fitness
- _ [testosterone] or menopause
- Partly responsible for: - _leanbodymass
- _ protein synthesis
- _metabolicrate
- _adiposetissue
- Evidence: (Giustina & Veldhuis, 2008)
- Excessive somatostatin release
- _/deficiency GHRH secretion in aging human
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Other names for Growth Hormone
Protein anabolic hormone
Lipolytic hormone
Diabetogenic hormone
Growth promoter hormone _
15
Relate GH to Linear Bone Growth
GH >> INC chondrocytic & osteogenic cell reproduction; INC protein deposition; Chondrocyte - osteogenic cells >> Chondrogenesis/Osteogenesis >> Linear Bone Growth
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Linear Bone Growth does not happen when the epiphyseal plates close. True or False?
TRUE
17
GH >> Unfused Epiphyses results to:
Gigantism
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GH >> Fused Epiphyses results to:
Acromegaly
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Effect of Growth Hormone on Protein Metabolism (ANABOLIC)
Stimulates AA uptake & CHON deposition
- _proteinbreakdown
- Effect begins in minutes
- Stimulates collagen synthesis+A19
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Protein metabolism produces what products
(+) Nitrogen balance _BUN&AA _excretionofAA4-hydroxyproline
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Effect of Growth Hormone on Electrolyte Metabolism
_ GI absorption of Ca2+
_ Na+ and K+ excretion most probably due to diversion from kidneys to growing tissues (+) P balance; _ plasma P
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Effect of Growth Hormone on Carbohydrate Metabolism
Normal GH level needed to maintain normal pancreatic islet function >> decreased insulin if no GH | DEC CHO use >> Diabetogenic
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GH-induced insulin resistance/hyperglycemia results to:
DEC Glucose uptake by tissues| INC insulin secretion | INC hepatic gluconeogenesis
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Effect of Growth Hormone on Fat Metabolism
Lipolytic
_ FA mobilization & use for energy
_ FA to Acetyl CoA conversion
_ FFA may contribute to GH-induced insulin resistance
EXCESSIVE GH >> Large quantities of fat metabolized >> Liver >> Ketosis/Fatty Liver
25
GH promotes diabetogenic state. True or False
TRUE
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Summary of GH Actions
_ protein synthesis rate in most body cells
_ Adiposity:
_ lipolysis / FA mobilization from adipose tissue _ FA in blood
_FA use as fuel
_ glucose uptake
_ linear growth
_ organ size & function
_lean body mass
27
Relate how GH >> Adipose Tissue >> DEC Adiposity
GH -> Adipose Tissue >> _ glucose uptake (hyperglycemic hormone)
_ lipolysis >> _ adiposity
28
Relate how GH >> Liver >> Facilitation of GH effect on:
organs (size & function) muscle (body mass) chondrocytes (linear growth)
GH -> Liver >> _ RNA synthesis
_ protein synthesis _ gluconeogenesis _ IGF/somatomedin >> Facilitation of GH effect on: organs (size & function) muscle (body mass) chondrocytes (linear growth)
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Relate how GH >> Muscle >> INC lean body mass
GH -> Muscle >> _ glucose uptake _ AA uptake
_ protein synthesis >> _ lean body mass
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