Download Endocrine system

Introduction to the
endocrine system
Ziying WANG
Institute of Pharmacology
School of Medicine,
Shandong University
[email protected]
Part 1 Introduction
Endocrinology
1. Definition: the study of hormones and
their functions.
2. History:
(1)
(2)
(3)
(4)
Ancient China
1849, Berthold
1855, Addison’s disease
Ernest Starling
1902, Hormone,
1905, “Endocrine system”
Ernest Starling
(1866-1927)
Endocrine vs. exocrine
Characteristic of endocrine gland
• Without duct
• The endocrine cells
arranged in cluster,
follicle or cords
• Rich in capillaries
• The secretion is
hormone which
transported by
blood circulation
Endocrine system
1. Endocrine glands
(1) Classical endocrine glands
(2) Extensive endocrine glands
2. Endocrine cells
Classical endocrine glands
Hormones
Definition
-- chemical messengers
-- secreted by endocrine gland or cells
-- released into the blood
-- effect on target cells through receptors
Major Hormones
Hormones
Functions
• to control the regulatory systems in the body
(1) homeostasis
(2) metabolism
(3) growth and development
(4) reproduction
Endocrine vs. Nervous regulation
Endocrine regulation
-broadcasts its hormonal
messages to essentially all cells
-by secretion into blood and
extracellular fluid
-requires a receiver to get the
message
-slow and wider
Neural regulation
-exerts point-to-point
-control through nerves
-electrical in nature and fast
Neuroendocrine regulation: 1928, Scharrer
Transportation of Hormones
Endocrine (Telecrine, hemocrine)
Paracrine
Transportation of Hormones
Types of hormones
1. Peptide hormones
2. Steroids
3. Amine hormones
(derivatives of the amino acid tyrosine)
Synthesis of hormones
Synthesis of
peptide hormones
Synthesis of
steroid hormones
Synthesis of
amine hormones
The comparison of hormones
Receptors
Carrier
protein
Orally
active
storage
Peptides
Cell
No
membrane
Not usually
Hormone
Steroids
Cytoplasm Yes
/nucleus
Yes, mostly
Precursor
Thyroid
hormone
nucleus
Yes
Precursor
No
Hormone
Yes
Catecholamines Cell
No
membrane
The transport of hormones
1. Peptide and CA: water-soluble
2. Steroids and thyroid hormone:
bound to proteins
Eg. Thyroid hormones binding globulin (THBG)
Cortisol binding globulin (CBG)
Sex hormones binding globulin (SHBG)
Effects of hormone binding proteins:
(1) Increase the solubility
(2) Create an accessible reserve
(3) Increase the biological half time
The metabolism of hormones
1. Peptide hormones: degradation in a lysosome
2. Steroids: excreted in an unchanged form
3. Catecholamines: COMT and MAO
4. Thyroxine: removing the iodine residues
Results of metabolism
(1) Inactivation
(2) Activation
Properties of the hormone effect
1. Specificity
2. Signal transmission
3. High biological efficiency
Properties of the hormone effect
1.Specificity: target, receptor
Properties of the hormone effect
2. Signal transmission
Properties of the hormone effect
3. High Biological Efficiency
Low plasma concentration
(nmol – pmol/L)
→great regulatory function
Part 2 Important concepts in
endocrine regulation
Patterns of hormone secretion
Different hormones have markedly different
patterns of secretion.
1. Set point regulation
2. Episodic secretion
3. Diurnal variation
Regulation of hormone secretion:
endocrine axis
Endocrine axis
Regulation of hormone secretion:
negative feedback
1. Long-loop feedback:
(1) Classical negative feedback
(2) Regulated by the end product
2. Short-loop feedback
Regulated by the intermediate product
3. Ultrashort-loop feedback
Regulation of hormones secretion
Interaction Between the Hormones
• 1. Synergistic effects
• 2. Permissive effect
• 3. Antagonist effects
Interaction Between the Hormones
• 1. Synergistic effects
(1) Additive: same effect of the hormones
on one target organ
(2) Complementary: work on different
stages of a physiological procedure
Interaction Between the Hormones
• 2. Permissive effect
• A hormone enhances the responsiveness
of a target organ to the second hormone,
and increases the activity of the second
hormone.
Interaction Between the Hormones
3. Antagonist effects
• One hormone antagonize the effects of
another.
• Eg. The regulation effect of glucagon and insulin on
blood glucose metabolism
Part 3 Endocrine disorders
Endocrine disorders
• Normal amount of hormones are
essential for the body.
• Either excessive or insufficient
hormones secretion are disorders.
• Excessive secretion: hyper• Insufficient secretion: hypo-
Endocrine disorders
Secondary:
Hypothalamus or
pituitary disorder
Primary: endocrine
glands disorder
Endocrine disorders
Part 4 Endocrine investigations
General principles
1. Purposes: diagnosis/monitoring
2. After clinical pattern recognition or
understanding of physiology and anatomy
3. Blood test maybe basic or dynamic.
1) Basic test : 9:00h, fasted
2) Dynamic test:
(1) stimulation test :when suspect a hormone is too low.
(2) suppression test: when suspect a hormone is too high.
Measurement of hormones
1. Biological sample
(1) Blood
(2) Urine
(3) Biopsy
2. Image:
radiological imaging
is vital.
Ectopic hormone secretion
1. Definition: The inappropriate secretion of
hormones by tissues that do not usually
produce that hormones.
2. Clinical significance: as a feature of
endocrine tumors.
3. Diagnosis: combined methods.
Receptors and hormone action
The first step of a hormone’s action
is to bind to specific receptors at the
target cell.
Receptors of hormones
Protein in nature
(may contain carbohydrate or phospholipid moieties)
Classification by location:
1. Cell surface receptors
2. Intracellular receptors:
(1) cytoplasm receptors
(2) nucleus receptors
Receptors of hormones
Classification by mechanisms:
Mechanism of hormones action
1.Second messenger mechanisms:
Peptide hormones and CA
--bind the receptors on the membrane
--activate some enzyme on the membrane
-- regulate the concentration of second
messengers in the cytoplasm
G-protein-coupled Receptor
Second messenger mechanisms
Mechanism of hormones action
2. Gene expression mechanism:
Intracellular receptors
(1) --bind the receptors in the cytoplasm
-- HR complex goes into nuclear
Or -- bind the receptors in the nuclear
(2) -- bind to target DNA
(3) – regulate transcription
Gene expression mechanism
Gene expression mechanism
cytoplasm receptors
nucleus receptors
Mechanism of hormones action
3. Receptors activate a protein kinase
For insulin or growth hormone receptors