Animal Science 434 Reproductive Physiology

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Animal Science 434Reproductive Physiology

• Lecture 6 and 7 Endocrinology

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What is the function of the endocrine system?
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Integration of Body Functions

• nervous and endocrine system are similar
• nervous system
• seconds
• endocrine system
• minutes and hours

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Neuro-endocrine Response
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Manipulation of the Endocrine System

• Hormones can be used to regulate body functions
• growth (anabolic steroids)
• lactation (GH or STH)
• birth control (Estradiol, Progesterone)
• estrous cycle (PGF2?)
• superovulation and embryo transplant (FSH,eCG)
• parturition (oxytocin)

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Endocrine Gland

• A ductless gland
• Secretes substances (hormones) into blood or
  lymph that affect cells elsewhere in the body
• The secretion does not involve loss of tissue

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Exocrine Gland

• A gland with ducts that are used for secretion

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Hormone

• Substance produced by endocrine gland
• Acts on cells, tissues or organs at a place other
  than where produced
• Acts as a catalyst.

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Endocrine Glands
Ovary
Hypothalamus
Adrenal
Pineal
Uterus
Pituitary
Placenta
Testes (in bull)
Thyroid
Pancreas
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Classification and Properties of Hormone

• A. Site of Production
• B. Type of action
• 1. Primary hormone of reproduction
• 2. Metabolic hormone
• C. Chemical Structure
• 1. General structure
• Proteins and polypeptides
• Steroids
• Fatty acids
• Modified amino acid
• 2. Size

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Classification and Properties of Hormone

• A. Site of Production
• B. Type of action
• 1. Primary hormone of reproduction
• 2. Metabolic hormone
• C. Chemical Structure
• 1. General structure
• Proteins and polypeptides
• Steroids
• Fatty acids
• Modified amino acid
• 2. Size

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Location of the Hypothalamus and Pituitary Gland
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Hypothalamus
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Function of Hypothalamus

• appetite
• thirst
• body temperature
• vasomotor activity
• emotion
• use of body nutrient reserves
• activity of intestine
• sleep
• sexual behavior
• Production and release of releasing hormones

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Releasing Hormones of the Hypothalamus

• A. Structure
• short chain polypeptides (3 - 44 amino acids)
• B. General Function
• to cause the release of trophic hormones from the
  anterior pituitary gland

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Releasing Hormones of the Hypothalamus

• C.Hormones
• Gonadotropin releasing hormone (GnRH)
• LH, FSH release
• Thyrotrophin releasing hormone (TRH)
• TSH and prolactin release
• Corticotrophin releasing hormone (CRH)
• ACTH release
• Growth hormone releasing hormone (GH-RH)
• Somatostatin (growth hormone inhibiting hormone)

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Hypothalamus
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Cells of the Anterior Pituitary
Hypothalamus
Preoptic nuclei cell
Nerve Cells
Superior hypophyseal artery
Capillary plexus
Hypophyseal portal vessels
Posterior pituitary

• LH
• FSH
• Prolactin
• STH
• TSH
• ACTH

Capillary plexus
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Anterior Pituitary Hormones

• A. Structure
• 1. glycoproteins or proteins
• B. Hormones
• 1. gonadotropins
• Follicle stimulating hormone (FSH)
• Luteinizing hormone (LH)
• Prolactin

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Anterior Pituitary Hormones

• 2.Other trophic hormones
• Adrenal Corticotropin (ACTH)
• thyroid stimulating hormone (TSH)
• growth hormone (GH or STH)

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Structure of LH, FSH and TSH

• Made of 2 amino acid chains
• a chains are the same
• b chains differ and give specificity

a
S
S
b
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Anterior Pituitary
Hypothalamus
Supraoptic nuclei cell
Paraventricular nuclei cell
Nerve Cells
Capillary plexus
Posterior pituitary

• Oxytocin
• ADH

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Hypothalamus
Nuclei that produce posterior pituitary hormones
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Posterior Pituitary Hormones

• A.Structure
• polypeptides (9 amino acids)
• B. Hormone
• Oxytocin - contraction of smooth muscle

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Placental Hormones

• A. Equine Chorionic Gonadotropin (eCG)
• 1. FSH-like activity (some LH)
• 2. long half-life
• 3. In blood and not urine
• 4. Function
• stimulates follicular growth during pregnancy
• LH-like activity stimulates follicles to form
  accessory CLs

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Placental Hormones (cont.)

• Other commercial hormones from the equine
  placenta
• Estrogens (several)
• Found in mare urine
• Premarin is commercial name
• Treatment of postmenopausal women
• Estrogen replacement therapy
• Prevents osteoporosis
• Reduces heart disease

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Placental Hormones (cont.)

• B. Human Chorionic Gonadotropin (HCG)
• 1. LH-like activity.
• 2. In blood and urine.
• 3. Function
• prevents CL regression
• C. Placental Lactogen (PL)
• Has both GH- and prolactin-like activity.
• Development of mammary gland

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Gonadal Polypeptide Hormones

• A. Relaxin
• Secreted by CL during pregnancy.
• Prior estrogen exposure required
• Functions
• cervical dilation
• inhibits uterine contractions

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Gonadal Polypeptide Hormones

• B. Inhibin
• Male - Sertoli cells
• Female - granulosa cells
• Function
• inhibits FSH secretion without altering LH
  secretion

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Gonadal Steroids

• A. General
• 1. Origin - ovary, testis, adrenal
• 2. Structure

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SteroidSynthesis
Cholesterol
Pregnenolone
27-C
21-C
OH
Estradiol
18-C
HO
19-C
21-C
Progesterone
Testosterone
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Gonadal Steroids Cont.

• B.Androgens
• 1. Testosterone.
• Source
• Male - Leydig cells
• Female - theca interna
• Adrenal
• Bound in blood

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Gonadal Steroids cont.

• Function in the male
• spermatogenesis
• epididymis
• accessory sex glands and secondary sex organs
• male secondary sex characteristics
• anabolic activity
• inhibits GnRH and LH release

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Gonadal Steroids Cont.

• C. Estrogens
• Estradiol.
• Female - granulosa cells, placenta, adrenal
• Male - Sertoli cells, adrenal
• Transported in blood by steroid binding globulin

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Gonadal Steroids Cont.

• 4.Functions
• CNS
• Uterus growth
• Uterus contraction
• female secondary sex characteristics
• mammary gland
• stimulates or inhibits GnRH and LH release
• nonreproductive
• a. calcium uptake and bone ossification
• b. anabolic and growth effects

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Gonadal Steroids Cont.

• D. Progestins
• 1. An example is progesterone
• 2. Produced in the CL, the placenta and the
  adrenal gland.
• 3. Transported in the blood bound to steroid
  binding globulin.
• 4. Functions
• prepares the uterus for implantation and
  pregnancy
• acts with estrogen to induce the behavior
  patterns of estrus
• develops alveoli of mammary gland
• inhibits the rise of LH that causes ovulation by
  inhibiting GnRH and LH release

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SteroidSynthesis
Cholesterol
Pregnenolone
Mitochondria
OH
Estradiol
Smooth ER
HO
Progesterone
Testosterone
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Other Hormones

• A. Prostaglandins
• 1. An example is PGF2a

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Lipid Hormones - Prostaglandins
Fatty Acids
Prostaglandins 1. Produced by all tissues of
body 2. Can have a local effect on tissues
(same tissue which produced it) 3. Rapidly
degraded in lungs
Phospholipids
- Rate limiting (Phospholipase A2)
- Precursor to Prostaglandins
Arachidonic Acid
Cyclo-oxygenase

• Vasoconstriction
• CL regression
• Ovulation
• Parturition
• Sperm transport

• Vasodilation
• Maintain CL
• Ovulation
• Implantation

PGF2a
PGE2
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Other Hormones

• B. Melatonin
• 1. Secreted from the pineal gland.
• 2. Is a modified amino acid
• 3. Functions to integrate effects of light on
  reproductive processes.

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Other Hormones

• C. Human Menopausal Gonadotropin (hMG)
• Anterior pituitary gland
• menopause.
• FSH-like activity
• long half-life.
• no estradiol feedback.
• In urine
• Perganol

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Classification and Properties of Hormone

• A. Site of Production
• B. Type of action
• 1. Primary hormone of reproduction
• (FSH, LH, estradiol, progesterone)
• 2. Metabolic hormone
• (thyroxin, insulin, STH)

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Classification and Properties of Hormone

• Chemical Structure
• Polypeptides - hypothalamic
• Protein - pituitary, gonad
• Steroids - gonad, adrenal
• Fatty acid - many sources, prostaglandins
• Modified amino acid - pineal

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Chemical Structure of Hormones
polypeptide modified amino acid protein sex
steroid fatty acid GnRh melatonin LH
Estradiol PGF TRH FSH Progesterone CRH Prolact
in Testosterone GHRH ACTH Somatistatin TSH Oxyto
cin GH or STH Relaxin Inhibin
2?
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Chemical Structure of Hormones
Molecular size of hormones that regulate
reproduction
Hormone Molecular Weight

• FSH 30,000 to 37,000
• LH 26,000 to 32,000
• Prolactin 23,000 to 25,000
• HCG 37,700
• eCG 28,000
• Relaxin 6,500
• ACTH 4,500
• Inhibin gt10,000
• Oxytocin 1,007
• GnRH 1,200
• Estradiol 300
• Testosterone 300
• Progesterone 300
• PGF 300

2?
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Chemical Structure of Hormones Cont.

• Polypeptide and protein hormones
• are made of peptide bonds

These hormones can not be given orally!
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Chemical Structure of Hormones Cont.

• Steroids

PROGESTERONE
CORTISOL
These hormones can be given orally!
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Mechanism of Hormone Action
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Mechanism of Hormone Action
Protein Hormones (cAMP second messenger)
Adenylate cyclase
phosphorylation of enzymes in steroid synthesis
Mitochondria
Cholesterol
Protein synthesis that regulates steroid
synthesis (enzymes)
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cAMP Second Messenger Hormones

• Anterior Pituitary Hormones
• LH, FSH, Prolactin
• STH, ACTH, TSH
• Placental Hormones
• HCG, eCG

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Protein Hormones (Ca2 Second Messenger)
GnRH
Plasma
Membrane
Phosphotidyl
Inositol
Receptor
G-protein
Receptor
DAG
R
Endoplasmic Reticulum
Secretory
Granules
Fusion
Plasma Membrane
LH
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Calcium Second Messenger Hormones

• GnRH
• triggers release of LH in anterior pituitary
• Oxytocin
• triggers contractions of smooth muscle
• PGF2?
• triggers apoptosis of cell
• inhibition of progesterone synthesis

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Receptor Structure
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Steroid Hormone Action
Uterine Growth
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Feedback Loops
Neuro-secretory Cells
Hypothalamus
Releasing Hormones
Polypeptides
Portal Vein
-
Anterior Pituitary
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Gonadotropins FSH, LH
Proteins
Blood Stream
Gonads
Why only effects on


Receptor on Cell Surface
target organs
Cyclic AMP inside cell
Testosterone

Steroid Hormone Production
Estradiol
Progesterone
Blood Stream
Bound to Protein