The endocrine system is composed of organs positioned throughout the body in widely separated locations. Endocrinology is the study of the structure and functioning of the endocrine system.

1. THE ENDOCRINE SYSTEM

2. Endocrine system
 Composed of organs positioned throughout
the body in widely separated locations.
 ENDOCRINOLOGY – the study of the
structure and functioning of the endocrine
system.

3. Integration of body functions
 Nervous and endocrine systems are integral
 Nervous system
Seconds
 Endocrine system
Minutes, hours, years

4. Hormone
 Substance produced in one tissue, secreted
into the blood and transported by the
vascular system to a distant target tissue,
where it exerts its effect.

5. Importance
 Hormones can be used to regulate body functions
 Growth (anabolic steroids)
 Lactation (GH or STH)
 Birth control (Estradiol, Progesterone)
 Estrus cycle (PGF2α)
 Superovulation and embryo transfer (FSH, eCG)
 Parturition (oxytocin)

6. Testes
Uterus
Adrenal
Ovary
Pineal

7. Brain diagram of endocrine glands

8. Stimulus
Sensory
neurons
Transmission
Efferent
neurons

9. Efferent
neurons
Hypothalamus
Neurohormone
Blood
Target tissue
Response by
target tissue

10. Suckling reflex
Suckling
Sensory
neurons
Transmission
Efferent
neurons

11. Suckling reflex
Hypothalamic
neurons
Oxytocin Blood
Mammary
Gland

12. Properties of hormones
 Act in minute amounts
 Have short half-lives
 Bind to specific receptors
 Regulate intracellular biochemical reactions

13. Classifications of hormone
 Source (glandular origin)
 Mode of action
 Biochemical classification

14. Source
 Hypothalamic hormones – GnRH
 Pituitary hormones – FSH, LH, prolactin
 Gonadal hormones – estrogen, testosterone
 Others (uterus, placenta) – PGF2α,
progesterone

15. Mode of action
 Neurohormone – oxytocin
 Releasing hormones – GnRH
 Gonadotropins – FSH, LH
 Sexual promoters – estrogen, testosterone,
progesterone
 Placental hormones – hCG, eCG

16. Mode of action
 Pregnancy maintenance hormones
Progesterone, placental lactogen
 General metabolic hormones
Thyroxin, corticosteroids, GH
 Luteolytic hormones – PGF2α

18. Biochemical structure
 Peptides – GnRH
 Glycoproteins – FSH, LH, TSH
 Prostaglandins – PGF2α, PGE2
 Steroids – estradiol, testosterone,
progesterone

19. Chemical Structure of Hormones Cont.
Polypeptide and protein hormones are made of peptide bonds
These hormones can not be given orally!
N C C
H
H
H
O
R
N C C
H H
O
R
Peptide Bond O
H

21. Chemical Structure of Hormones Cont.
Cholesterol
Pregnenolone
Progesterone
Testosterone
Estradiol
Cortisol
Progesterone
Ovary or TestisAdrenal
These hormones can be given orally!!!
Steroid
Biosynthesis

22. COOH
o
o
COOH
OOH
o
o
COOH
OH
O
OH
COOH
OH
COOH
OHOH
OH
Prostaglandins
•Many tissues
•Local effects
•Degraded in lung
Phospholipids
PLA2
Cyclo-oxygenase
Inhibited by
aspirin
PGE2 PGF2
PGH2
PGG2
Arachidonic Acid

23. COOH
o
o
COOH
OOH
o
o
COOH
OH
O
OH
COOH
OH
COOH
OHOH
OH
Phospholipids
PLA2
Cyclo-oxygenase
•Vasodilation
•Maintain CL
•Ovulation
•Implantation
•Vasoconstriction
•CL regression
•Ovulation
•Parturition
•Sperm transport
PGE2 PGF2
PGH2
PGG2
Arachidonic Acid

24. Chemical Structure of Hormones
Polypeptide Modified amino acid Protein Sex steroid Fatty acid
GnRh melatonin LH Estradiol PGF
TRH FSH Progesterone
CRH Prolactin Testosterone
GHRH ACTH
Somatistatin TSH
Oxytocin GH or STH
Relaxin
Inhibin
2

25. Location of the hypothalamus & pituitary gland

26. Hypothalamus

27. Functions of the hypothalamus
 Appetite
 Thirst
 Body temperature
 Vasomotor activity
 Use of body nutrient reserves
 Sleep
 Sexual behavior
 Production and release of releasing hormones

28. Releasing hormones of the hypothalamus
 Structure
 Short chain polypeptides (3 - 44 amino acids)
 General Function
 To cause the release of trophic hormones from the
anterior pituitary gland

29. Releasing hormones of the hypothalamus
 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)

30. Hypothalamus

31. Cells of the
Anterior Pituitary
• LH
• FSH
• Prolactin
• STH
• TSH
• ACTH
Hypothalamus
Nerve
Cells
Superior
hypophyseal
artery
Hypophyseal
portal
vessels
Capillary
plexus
Posterior
pituitary
Capillary
plexus
Preoptic
nuclei
cell

33. Anterior pituitary hormones
 Structure
 Glycoproteins or proteins
 Hormones
 Gonadotropins
 Follicle stimulating hormone (FSH)
 Luteinizing hormone (LH)
 Prolactin

34. Anterior pituitary hormones
 Other trophic hormones
 Adrenocorticotropin (ACTH)
 Thyroid stimulating hormone (TSH)
 Growth hormone (GH or STH)

35. Hypothalamus
Nerve
Cells
Posterior
pituitary
• Oxytocin
• ADH
Paraventricular
nuclei cell
Supraoptic
nuclei cell
Anterior
Pituitary
Capillary plexus

36. Hypothalamus
Nuclei that produce
posterior pituitary
hormones

38. Posterior pituitary hormones
 Structure
 Polypeptides (9 amino acids)
 Hormone
 Oxytocin – contraction of smooth muscle

39. Gland Hormone Principal Functions
Hypothalamus Gonadotropic Releasing
Hormone (GnRH)
Stimulates release of FSH and
LH from anterior pituitary
Dopamine Inhibits release of prolactin
Corticotropic Releasing
Hormone (CRH)
Stimulates ACTH release
Growth Hormone-Releasing
Hormone (GRH)
Stimulates release of growth
hormone
Oxytocin Produced by the
hypothalamus,
released at the posterior
pituitary.

40. Gland Hormone Principal Functions
Posterior Pituitary Oxytocin Stimulate myometrial contractions for
sperm transport, parturition & milk
ejection
Anterior Pituitary Follicle Stimulating Hormone(FSH)
- Follicotropin
Stimulate follicle growth Stimulate
estrogen production
Spermiogenesis in male
Luteinizing Hormone (LH) -
Luteotropin
Stimulate ovulation
Support CL formation, and progesterone
secretion Stimulate testosterone synthesis
by leydig cells of testis
Prolactin Stimulate milk synthesis
Regulate metabolism for milk synthesis
Effects maternal behavior
Adrenalcorticotropic
Hormone(ACTH)
Release of corticosteroids &
glucocorticoids from adrenal cortex to
initiate parturition

41. Gland Hormone Principal Functions
Ovary
Graafian Follicle
Estrogens (Estradiol) Mating behavoir,
Secondary sex
characteristics,
Maintenance of female
duct system , Mammary
growth
Inhibin (Folliculostatin)
Regulates release of FSH
from anterior pituitary
Corpus Luteum Progestins (Progesterone) Maintenance of
pregnancy, Mammary
growth & secretion
Relaxin Expansion of pelvis
Dilation of cervix

42. Gland Hormone Principal Functions
Testis
Leydig Cells
Androgens (Testosterone) Male mating behavior,
Spermatocytogenesis,
Maintenance of male
duct system & accessory
glands
Sertoli Cells Inhibin Regulates release of
FSH
Adrenal Cortex Glucocorticoids (Cortisol) Induction of parturition
by fetus
Milk synthesis
Stress response

43. Gland Hormone Principal Functions
Placenta Human Chorionic
Gonadotropin(HCG)
LH-like - Involved with
establishment of pregnancy in
human. Support and maintain CL
Endometrial Cups
Mare
Equine Chorionic Gonadotropin(eCG)
Old name - Pregnant Mare Serum
Gonadotropin (PMSG)
FSH-like- some LH activity
Immunological protection of foal
during pregnancy Formation of
accessory CL in mare
Estrogens/Progestins Regulate placental bloodflow
Maintenance of pregnancy
Relaxin Relaxation/dialation of cervix for
parturition
Placenal Lactogen Stimulates mammary growth &
milk secretion.

44. Gland Hormone Principal Functions
Uterine Endometrium
Graafian Follicles
Seminal Vesicles
Prostaglandin F2a (PGF2a) Regression of CL
Stimulate myometrial
contractions
Ovulation
Sperm transport
Pineal Gland Melatonin Control of seasonal
reproduction in Mare &
Ewe
Regulate hair growth