Animal Science 434
Reproductive Physiology
Lecture 6 and 7:
Endocrinology
What is the function of the
endocrine system?
Integration of Body Functions
• nervous and endocrine systems are similar
• nervous system
»
seconds
»
minutes and hours
• endocrine system
Neuro-endocrine Response
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)
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
Exocrine Gland
• A gland with ducts that are used for
secretion
Hormone
• Substance produced by endocrine gland
• Acts on cells, tissues or organs at a place
•
other than where produced
Acts as a catalyst.
Endocrine Glands
Hypothalamus
Pineal
Adrenal
Ovary
Uterus
Pituitary
Placenta
Testes
(in bull)
Thyroid
Pancreas
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
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
Location of the Hypothalamus and Pituitary
Gland
Hypothalamus
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
Releasing Hormones of the Hypothalamus
A.
B.
•
•
Structure
short chain polypeptides (3 - 44 amino acids)
General Function
to cause the release of trophic hormones from the
anterior pituitary gland
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)
Hypothalamus
Hypothalamus
Preoptic
nuclei
cell
Nerve
Cells
Superior
hypophyseal
artery
Capillary plexus
Hypophyseal
portal vessels
Cells of the
Anterior
Pituitary
•
•
•
•
•
•
LH
FSH
Prolactin
STH
TSH
ACTH
Posterior
pituitary
Capillary
plexus
Hypothalamus and
Anterior Pituitary Gland
Anterior Pituitary Hormones
A. Structure
1. glycoproteins or proteins
B. Hormones
1. gonadotropins
» Follicle stimulating hormone
» Luteinizing hormone (LH)
» Prolactin
(FSH)
Anterior Pituitary Hormones
2.Other trophic hormones
•
•
•
Adrenal Corticotropin (ACTH)
thyroid stimulating hormone (TSH)
growth hormone (GH or STH)
Structure of LH, FSH and TSH
•
Made of 2 amino acid chains

S
•
•
S
b
 chains
are the same
b chains differ and give specificity
Hypothalamus
Supraoptic
nuclei cell
Nerve
Cells
Paraventricular
nuclei cell
Capillary plexus
Anterior
Pituitary
Posterior
pituitary
• Oxytocin
• ADH
Hypothalamus
Nuclei that produce
posterior pituitary
hormones
Posterior Pituitary Hormones
A.Structure
• polypeptides (9 amino acids)
B.Hormone
•
Oxytocin - contraction of smooth muscle
Placental Hormones
• Equine
Chorionic Gonadotropin (eCG)
» Formation of accessory CL and maintains
pregnancy
• Human
Chorionic Gonadotropin (HCG)
»
Maintains primate CL and pregnancy
»
Development of the mammary gland in the
mother
• Placental
• Steroids
Lactogen (PL)
- Estrogen and Progesterone
Gonadal Polypeptide Hormones
•
Relaxin
» Secreted by CL during pregnancy.
» Parturition
•
Inhibin
» Inhibits FSH release
Gonadal Steroids
A. General
»
»
Origin - ovary, testis, adrenal
Structure
Steroid
Cholesterol
27-C
Synthesis
Pregnenolone
21-C
OH
Estradiol
18-C
HO
19-C
21-C
Progesterone
Testosterone
Gonadal Steroids Cont.
A. General Cont.
» Solubility
– Bound to a binding protein for transport
B. Type of Steroids
» Androgens - Testosterone
» Estrogen - Estradiol
» Progestin - Progesterone
Steroid
Cholesterol
Synthesis
Pregnenolone
Mitochondria
OH
Estradiol
HO
Smooth ER
Progesterone
Testosterone
Other Hormones
A. Prostaglandins
1. PGF2
2. PGE2
Phospholipids
Prostaglandins
PLA2
•Many tissues
•Local effects
•Degraded in lung
PGG2
COOH
Arachidonic Acid
o
o
COOH
Cyclo-oxygenase
Inhibited by
aspirin
COOH
•Vasoconstriction
•CL regression
•Ovulation
•Parturition
•Sperm transport
OOH
•Vasodilation
•Maintain CL
•Ovulation
•Implantation
O
OH
PGH2 o
o
OH
PGE2
OH
PGF2
COOH
COOH
OH
OH
OH
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.
Other Hormones
C. Human Menopausal Gonadotropin (hMG)
1. Anterior pituitary gland
» Secreted in menopause, FSH-like activity
» Isolated from urine
a. Perganol - superovulation
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)
Classification and Properties of Hormone
•
Chemical Structure
» Polypeptides - hypothalamic
» Protein - pituitary, gonad
» Steroids - gonad, adrenal
» Fatty acid - many sources, prostaglandins
» Modified amino acid - pineal
Chemical Structure of Hormones
polypeptide modified amino acid
GnRh
melatonin
TRH
CRH
GHRH
Somatistatin
Oxytocin
protein
sex steroid
fatty acid
LH
Estradiol
PGF2
FSH
Progesterone
Prolactin Testosterone
ACTH
TSH
GH or STH
Relaxin
Inhibin
Chemical Structure of Hormones
Molecular size of hormones that regulate reproduction
Hormone
FSH
LH
Prolactin
HCG
eCG
Inhibin
Relaxin
ACTH
Oxytocin
GnRH
Estradiol
Testosterone
Progesterone
PGF
2
Molecular Weight
30,000 to 37,000
26,000 to 32,000
23,000 to 25,000
37,700
28,000
>10,000
6,500
4,500
1,007
1,200
300
300
300
300
Chemical Structure of Hormones Cont.
Polypeptide and protein hormones
are made of peptide bonds
NH 3
R
CH
C
O
HC
R
HN
O
Peptide
Bond
C
NH
R
CH
COO-
These hormones can not be given orally!
Chemical Structure of Hormones Cont.
Steroids
CHOLESTEROL
PREGNENOLONE
ADRENAL
OVARY OR TESTES
CORTISOL
PROGESTERONE
PROGESTERONE
 OH-PROGESTERONE
CORTISOL
ANDROSTEINDIONE
TESTOSTERONE
ESTRONE
ESTRADIOL
These hormones can be given orally!
Mechanism of Hormone Action
Mechanism of Hormone Action
Receptor Structure
Mechanism of Hormone Action
Protein Hormones
(cAMP second messenger)
LH
G
Receptor
Plasma Membrane
Adenylate Cyclase
cAMP
R cAMP
Testosterone
ATP
cAMP
S-ER
R
C
Steroid Synthesis
C
Protein Kinase A
(PKA)
(+ PO4)
Mitochondria
Cholesterol
Pregnenolone
Histones
Cholesterol
Protein
Synthesis
(Enzymes)
Synthesis
R-ER
Protein
mRNA
Nucleus
DNA
cAMP Second Messenger Hormones
•
Anterior Pituitary Hormones
•
Placental Hormones
» LH, FSH, Prolactin
» STH, ACTH, TSH
» HCG,
eCG
Protein Hormones (Ca2+ Second Messenger)
Ca2+
Plasma
Membrane
Receptor
GnRH
G-protein
PIP2
DAG
PLC
IP3
Protein
Kinase C
Ca2+
R
Ca2+
Secretory
Granules
Endoplasmic Reticulum
Fusion
Plasma Membrane
LH
Calcium Second Messenger Hormones
•
GnRH
•
Oxytocin
•
PGF2
» triggers
» triggers
release of LH in anterior pituitary
contractions of smooth muscle
» triggers apoptosis of cell
» inhibition of progesterone
synthesis
Steroid Hormone Action
Steroid
(estrogen)
Cell Membrane
Diffusion?
Change in
Cell
Physiology
Cytoplasm
Nucleus
New
Protein
Receptor
R-ER
mRNA
Protein synthesis
DNA
Steroid Hormone Mechanism
•
•
•
Estradiol
Testosterone, Dihdrotestosterone
Cortisol
Hypothalamus
Feedback
Loops
Neuro-secretory Cells
Releasing Hormones
Polypeptides
Portal Vein
Anterior Pituitary
Gonadotropins: FSH, LH
Proteins
Blood Stream
Gonads
Receptor on Cell Surface
only effects on
[ Why
]
target organs
Cyclic AMP inside cell
Steroid Hormone Production
{
Testosterone
Estradiol
Progesterone
Blood Stream
Bound to Protein