PP30 Hormonal Regulation of Growth 3

1
PP30Hormonal Regulation of Growth 3

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

2
Hormones Influencing Growth Ovarian Hormones

• Ovaries estrogen from follicles
• Control
• LH and FSH by anterior pituitary
• (-) feedback from progesterone/inhibin
• () feedback of estrogen
• Actions indirect and direct
• General maturation of reproductive tract,
  female sex characteristics, mammary duct
  development and body growth

3
(No Transcript)
4
Hormones Influencing Growth Testicular Hormones

• Testes Testosterone from the Leydig cells
• Actions direct and indirect
• General maturation of reproductive tract, male
  sex characteristics, spermatogenesis and body
  growth

5
Hormones Influencing Growth
6
Muscle Cell
7
Hormones Influencing Growth Testosterone

• Prenatal high concentrations produced by fetus
• Bone
• Increases long bone growth in young animals via
  incorporation of cartilage
• Accelerates epiphyseal plate closure in animals
  after puberty by influencing chondrocyte
  proliferation and function
• Influences interaction between osteoblasts and
  osteoclasts activity by coupling bone formation
  and reabsorption

8
(No Transcript)
9
Hormones Influencing Growth Testosterone

• Muscle
• Direct stimulation of muscle growth to enhance
  protein synthesis
• Indirect results in decreased rates of
  degradation with variable effects on synthesis,
  which may be modulated through growth hormone
• Influences myogenesis by increasing the number of
  myoblasts formed resulting in increased muscle
  fiber numbers in males compared with females
• Fat
• Facilitates fat deposition in chickens

10
Hormones Influencing Growth Testosterone

• Birth low concentrations of testosterone after
  birth until puberty
• Postnatal increased concentrations just before
  and after puberty
• Bone
• Acts on periosteal osteoblasts to increase bone
  mass and cortical thickness
• Influences interaction between osteoblasts and
  osteoclasts activities by coupling bone formation
  and reabsorption

11
Hormones Influencing Growth Testosterone

• Postnatal
• Muscle
• Direct increases protein synthesis
• Indirect effects are mediated trough growth
  hormone with males having greater growth hormone
  than castrates
• Net actions increase protein accretion
• Synthesis gt Degredation
• May interfere with anti-anabolic effects of
  cortisol
• Fat
• Does not enhance fat deposition (lipolytic
  actions)

12
Hormones Influencing Growth Synthetic Hormones

• Primary use is to improve efficiency of gain in
  beef cattle
• Used in castrates because of behavioral problems
  with intact males
• Androgens
• Improves growth, feed conversion and increases
  protein content in cattle (also pigs)
• Most effective in heifers but also works in
  castrates

13
(No Transcript)
14
Hormones Influencing Growth Synthetic Hormones

• Androgens Estrogen
• Most effective in castrates
• Binding of estrogen and testosterone to skeletal
  muscle
• Increased protein accretion due to decreased
  protein degradation resulting in myofiber
  hypertrophy
• May increase recruitment of satellite cells

15
(No Transcript)
16
Hormones Influencing Growth Synthetic Hormones

• Residue Problem
• Little difference in beef from non-implanted
  castrates compared to implanted castrates
• Amount of steroid consumed in meat is less than
  what is found in normal human body

17
(No Transcript)
18
(No Transcript)
19
Hormones Influencing Growth Parathyroid Gland

• Parathyroid hormone (PTH) polypeptide
• Control
• Low Ca stimulates PTH release
• High Ca inhibits PTH release
• Action
• Increases serum Ca due to mobilization from bone

20
(No Transcript)
21
Hormones Influencing Growth Parathyroid Gland

• Calcitonin polypeptide secreted from
  parafollicular cells of thyroid gland
• Control
• Increased serum Ca stimulates its release
• Action
• Decreased release of Ca from bone
• Opposite effect of PTH
• Calcium Homeostasis

22
(No Transcript)