PP4 Endocrinology 3

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PP4 Endocrinology 3

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

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Review Hormone Actions

• Mode of action is through receptors that
  recognize specific hormones
• Receptors allow hormones to act on specific
  tissues
• Exhibit a high rate of secretion and a high rate
  of degradation within circulation
• Rate of secretion is variable

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Types of Hormone Secretion
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Classes of Hormones

• Proteins long chains of amino acids
• Growth Hormone
• Glycoproteins proteins with sugars attached
• Chorionic Gonadotropin
• Steroids Cholesterol is precursor
• Estrogen, Testosterone, Progesterone

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Classes of Hormones

• Peptides small chains of amino acids
• Releasing and inhibiting hormones
• Modified amino acids
• Thyroid hormones
• Fatty acid derivatives
• Prostaglandins
• Synthetic hormones

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Hormone Breakdown

• Biological activity is a direct function of how
  long the hormone is able to circulate in the body
  before being broken down
• Biolgical activity the strength and duration of
  a hormones physiological actions

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Hormone Breakdown

• Proteins are broken down faster than steroids
• Related to the amount of glycosylation
• Influences how exogenous hormones are
  administered
• Example insulin and growth hormone must be
  administered daily by injection, not given orally

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Hormone Signaling

• Negative feedback
• Hormone acting on a tissue sends a signal back to
  the hypothalamus or pituitary inhibiting further
  secretion
• Positive feedback
• Hormone acting on a tissue sends a signal back to
  the hypothalamus or pituitary promoting further
  secretion (more receptors, increased mRNA)
• Multiple hormone feedback

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Positive and Negative Feedback
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Multiple Feedback Systems
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Hormones

• Growth Hormone
• Protein hormone from the anterior pituitary
• Promotes tissue growth
• Promotes metabolism of muscle and bone
• Catabolic actions on adipose tissue
• Actions is mediated through Insulin-like Growth
  Factor-1 (IGF-1)
• IGF-1 produced primarily in the liver but also
  produced in other cells of the body

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Hormones

• Somatostatin
• Protein hormone from the anterior pituitary
• Growth Hormone Inhibiting Hormone
• Modulates/inhibits Growth Hormone secretion

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Hormones

• Thyroid Gland
• Thyroxin (T4) and Triiodothyronine (T3)
• Modified amino acids
• Enhance protein synthesis
• Increase general metabolism
• Calcitonin
• Modified amino acid
• Regulates calcium metabolism by decreasing
  calcium mobilization from the bone

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Hormones

• Parathyroid Gland
• Parathyroid Hormone
• Peptide hormone
• Regulates calcium and phosphorous metabolism
  primarily by increasing calcium mobilization from
  the bone
• Adipocyte
• Leptin
• Peptide hormone
• Regulates body energy stores (adipose tissue)
• Influences the secretion of hormones involved in
  adipose tissue metabolism

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Hormones

• Pancreas
• Insulin
• Protein Hormone From Beta Cells
• Regulates carbohydrate metabolism by increasing
  the storage of glucose, fatty acids and amino
  acids
• Anti-lipolytic actions
• Adrenal Medulla
• Epinephrine
• Modified amino acid
• Fight or flight response
• Catabolic effects on muscle and adipose to
  provide energy

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Hormones

• Adrenal Cortex
• Glucocorticoids (Steroids)
• Cortisol (mammals)
• Initiation of parturition, milk synthesis
• Decreased inflammatory and immunologic responses
• Catabolic actions on muscle and adipose tissue to
  enhance energy metabolism during stress and
  injury

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Hormones

• Ovary
• Estrogen
• Steroid
• From follicles
• Promotes female sex characteristics and behavior
• Promotes maintenance of female duct system and
  development of mammary gland
• Stimulates uterine contractions and secretions
  (influences PGF2a)
• Stimulates Ca uptake in bones and closure of
  epiphyseal plate
• Stimulates muscle growth (Species and gender
  specific)
• Facilitates fat deposition (Species and gender
  specific)

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Hormones

• Testis
• Testosterone
• Steroid
• Stimulates secondary sex characteristics and male
  mating behavior
• Stimulates the development and maintenance of
  male duct system and spermatogenesis
• Enhances growth and development of muscle and
  bone
• Inhibits fat deposition

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Hormones

• Placenta
• Placental Lactogen
• Glycoprotein
• Stimulates mammary growth and secretions
• Regulates nutrient flow to fetus