PP29 Hormonal Regulation of Growth 2

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PP29Hormonal Regulation of Growth 2

• Chapter 10 pg 179-198
• ANS 3043
• University of Florida
• Dr. Michael J. Fields

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Pancreatic Hormones Insulin

• Control
• Secretion controlled by (-) and () effects of
  other hormones and metabolites
• Secretion is enhanced by food intake and
  increased blood glucose
• Actions
• Increased uptake of glucose and amino acids
• Stimulation of lipogenesis, glycogenesis and
  protein synthesis
• Blood glucose is tightly controlled in ruminants,
  but not monogastrics

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Pancreatic Hormones Glucagon

• Control
• Enhanced by the () and (-) feedback of hormones
  and metabolites
• Secretion is enhanced by decreased food intake
  and decreased plasma glucose
• Actions
• Mobilizing glucose by increasing glycogenolysis
  and gluconeogenesis
• Mobilizing fatty acids by increasing lipolysis
• Increasing amino acid catabolism

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Pancreatic Hormones

• Short and long term stress response on glucose
  metabolism
• Epinephrine short term stress (fight or flight)
• Glucose needed immediately by muscles and other
  vital organs for energy
• Primarily from glycogen stores
• Cortisol long term stress (chronic)
• Glucose comes from metabolism of glycogen, muscle
  and fat
• Supplies energy for remainder of body,
  particularly if nutrient intake is decreased

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Hormones Affecting Metabolism Leptin

• Produced by adipose tissue
• Appears to be important in providing signals to
  hypothalamus that regulate multiple response
  mechanisms
• Increase in adipose tissue mass causes
• Increased concentrations of leptin, which induces
  hypothalamus to
• Decrease food intake
• Increase energy expenditure
• Modulate other hormones including insulin,
  cortisol and GH that decrease lipogenesis and
  increase lipolysis

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Hormones Affecting Metabolism Leptin

• Increased energy expenditure is a result of and
  increase in uncoupling protein (UCP) in adipose
  tissue mitochondria, which increases heat
  production
• Leptin induced mechanisms probably result in
  decreased adipose tissue mass

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Hormones Affecting Metabolism Prolactin

• Protein Hormone
• Major target organ is mammary gland
• Involved in mammary gland development
• Proliferation and differentiation of mammary
  tissues both pre and postnatal
• Important in protein synthesis during lactation

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Hormones Affecting Metabolism Prolactin

• Possible role in nutrient partitioning
• Net protein accretion
• Alters adipose tissue metabolism
• Evidence suggests that growth hormone effects may
  be modulated through prolactin
• Concentration vary directly with temperature and
  day length

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Hormones Affecting Metabolism Thyroid Hormones

• Secretion from thyroid gland
• Highly vascularized and bi-lobed gland located
  around trachea
• Structure
• Combination of tyrosine iodine
• T3 3, 5, 3I triiodotyronine and
• T4 3, 5, 3I, 5I tertaiodotyronine (Thyroxine)
• Iodine required for synthesis
• Biological activity T3 gt T4

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T4 - 3,5,3,5 triodotyronine - thyroxine
I
I
O
HO
CH2CH-COOH
NH2
I
I
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Hormones Affecting Metabolism Thyroid Hormones

• Control negative feedback
• Circulating hormone is transported and regulated
  by thyroid binding globulin
• T3 and T4 bind to nuclear receptors
• Function
• General physiology
• No specific target organs but influences
  oxidative metabolism and anabolic function in
  virtually all tissues
• Appears to be essential for CNS function

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Hormones Affecting Metabolism Thyroid Hormones

• Growth physiology anabolic and catabolic
  actions
• Potentiates insulins actions on carbohydrate
  meatbolism
• Increases protein syntehsis and nitrogen balance
  possibly through increased growth hormone release
• Stimulates lipid metabolism, both lipogenesis
  andlipolysis
• Lipolysis gtgtgtgtgtgtgt Lipogenesis
• Thermogenic actons
• Catabolic effects on proteins, CHO, and lipids to
  provide heat and energy

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Hormones Affecting Metabolism Thyroid Hormones

• Environmental conditions effects on release
• Long term cold stress causes enhanced release,
  which results in increased metabolic rate
• Mental and physical stress (Chronic)
• Release is inhibited

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Hormones Affecting Metabolism Thyroid Hormones

• Clinical Aspects
• Hypothyroidism (lack of)
• Particularly in fetal and young postnatal
  individuals
• Dwarfism and neurological disorders
• Hyperthyroidism (excess)
• Restless, irritable and high basal metabolic rate
• Weakness in muscle
• Exophtalmus protrusion of eyeballs

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Hormones Affecting Metabolism Adrenal Gland

• Located on dorsal aspect of kidney
• Consists of specific layers and highly
  vascularized and innervated
• Adrenal Medulla
• Produced catecholamines in response to severe
  acute stress
• Epinephrine and Norepinephrine
• Various vascular changes such as increased heart
  rate and blood flow
• Increased body temperature and respiration
• Induces anaerobic glycolysis to meet energy needs
  of skeletal muscle
• Epinephrine acts through beta adrenergic
  receptors
• Norepinephrine acts through alpha and beta 1
  adrenergic receptors

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Hormones Affecting Metabolism Adrenal Gland

• Synthetic beta-adenergic agonists
• Synthetic compounds that act via receptors and
  modify cellular metabolism
• Results in improved growth, feed conversion and
  efficiency of tissue deposition in ruminants and
  pigs
• Decreased fat deposition (decreased lipogenesis
  and/or increased lipolysis
• Increased muscle increased protein synthesis
  and changes in protein degradation possibly a
  result in satellite cell recruitment
• Ractopamine only beta-adrenergic agonist approved
  by FDA (used is swine)

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Hormones Affecting Metabolism Adrenal Cortex

• Adrenal Cortex
• Zona glomerlosa mineralocorticoids
• Zona Reticularis steriods
• Zona Fasiculata glucocorticoids

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Hormones Affecting Metabolism Adrenal Cortex

• Control
• Release is stimulated by ACTH from anterior
  pituitary
• Negative feedback on the hypothatlamus and
  anterior pituitary

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Hormones Affecting Metabolism Adrenal Cortex

• Actions
• Exerts permissive effects by enhancing actions of
  other hormones
• Catabolic effects
• Decreases muscle protein synthesis and increases
  muscle protein degradation to make amino acids
  available for glucose production
• Enhances lipolysis by enhancing catecholamine
  stimulated lipolysis
• Long term stress adaption
• Growth inhibitory (enhances GH secretion)
• Immune system suppression, which can cause health
  problems

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