1. Introduction to the endocrine system
Ziying WANG
Institute of Pharmacology
School of Medicine,
Shandong University

2. Part 1 Introduction

3. Endocrinology
1. Definition: the study of hormones and their functions.
2. History:
Ancient China
1849, Berthold
1855, Addison’s disease
Ernest Starling
1902, Hormone,
1905, “Endocrine system”
Ernest Starling
( )

4. Endocrine vs. exocrine

5. 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

6. Endocrine system Endocrine glands 2. Endocrine cells
Classical endocrine glands
Extensive endocrine glands
2. Endocrine cells

7. Classical endocrine glands

8. Hormones Definition -- chemical messengers
-- secreted by endocrine gland or cells
-- released into the blood
-- effect on target cells through receptors

9. Major Hormones

10. Hormones Functions to control the regulatory systems in the body
(1) homeostasis
(2) metabolism
(3) growth and development
(4) reproduction

11. 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

12. Neuroendocrine regulation: 1928, Scharrer

13. Transportation of Hormones

14. Endocrine (Telecrine, hemocrine)

15. Paracrine

16. Transportation of Hormones

17. Types of hormones Peptide hormones 2. Steroids Amine hormones
(derivatives of the amino acid tyrosine)

18. Synthesis of hormones Synthesis of peptide hormones
Synthesis of steroid hormones
Synthesis of amine hormones

19. The comparison of hormones
Receptors
Carrier
protein
Orally active
storage
Peptides
Cell membrane No
Not usually
Hormone
Steroids
Cytoplasm/nucleus
Yes
Yes, mostly
Precursor
Thyroid hormone
nucleus
Catecholamines

20. 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

21. 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
Inactivation
Activation

22. Properties of the hormone effect
1. Specificity
2. Signal transmission
3. High biological efficiency

23. Properties of the hormone effect
1.Specificity: target, receptor

24. Properties of the hormone effect
2. Signal transmission

25. Properties of the hormone effect
3. High Biological Efficiency
Low plasma concentration
(nmol – pmol/L)
→great regulatory function

26. Part 2 Important concepts in endocrine regulation

27. Patterns of hormone secretion
Different hormones have markedly different patterns of secretion.
1. Set point regulation
2. Episodic secretion
3. Diurnal variation

28. Regulation of hormone secretion: endocrine axis

29. Endocrine axis

30. 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

31. Regulation of hormones secretion

32. Interaction Between the Hormones
1. Synergistic effects
2. Permissive effect
3. Antagonist effects

33. 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

35. 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.

37. 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

38. Part 3 Endocrine disorders

39. 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-

40. Endocrine disorders Secondary: Hypothalamus or pituitary disorder
Primary: endocrine glands disorder

41. Endocrine disorders

42. Part 4 Endocrine investigations

43. 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.

44. Measurement of hormones
Biological sample
(1) Blood
(2) Urine
(3) Biopsy
2. Image:
radiological imaging
is vital.

45. Ectopic hormone secretion
Definition: The inappropriate secretion of hormones by tissues that do not usually produce that hormones.
Clinical significance: as a feature of endocrine tumors.
Diagnosis: combined methods.

46. Receptors and hormone action
The first step of a hormone’s action
is to bind to specific receptors at the
target cell.

47. Receptors of hormones Protein in nature Classification by location:
(may contain carbohydrate or phospholipid moieties)
Classification by location:
Cell surface receptors
Intracellular receptors:
(1) cytoplasm receptors
(2) nucleus receptors

48. Receptors of hormones
Classification by mechanisms:

49. Mechanism of hormones action
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

50. G-protein-coupled Receptor

51. Second messenger mechanisms

53. 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

54. Gene expression mechanism

55. Gene expression mechanism
cytoplasm receptors
nucleus receptors

56. Mechanism of hormones action
3. Receptors activate a protein kinase
For insulin or growth hormone receptors

57. Thank you