1. Nature of hormones

2. What is a hormone? Hormone Greek “I excite” or “I arouse”
Classical definition
Chemical messenger released by one type of cells and carried in the bloodstream to act on specific target cells
Modern definition
Includes factors produced and used locally without entering the blood stream

3. Endocrine factors Autocrine factors Paracrine factors
Released and carried in the blood
Classical hormones
Autocrine factors
Released and used by the same cells
Paracrine factors
Affect function of neighboring cells without entering the blood stream
Interstitial fluid

4. GnRH
Hypothalamus
FSH LH
Estradiol
Pituitary
gland
Ovary

5. Granulosa cells
Basement
membrane
Antrum
Oocyte
Theca externa
Theca interna

6. Granulosa
cells (GC)
Theca
cells (TC)
Basement membrane

7. General characteristics of hormones
Very low in concentrations
Ppb (ng/ml) or ppt (pg/ml)
Very specific receptor
One hormone, one receptor

8. Chemical nature of hormones
Classes
Lipids
Steroids
Eicosanoids
Proteins
Short polypeptides
Large proteins
Chemical modification through glycosylation
Amino acid derivatives

9. Steroid hormones Derivative of cholesterol Large molecule
Hydrocarbon ring
Highly hydrophobic
Source
Diet
De Novo synthesis
Found in cell membrane

10. Cholesterol and its derivatives
Vitamin D
Bile acid
Lipid digestion
Steroid hormones
Sex steroids
Adrenal steroild
All cholesterol derivatives contain sterol ring

11. Steroid hormones Origins Adrenal Gonads (testis and ovaries)
Mineralocorticoids
Affect mineral homeostasis
Glucocorticoids
Affect glucose metabolism and immune function
Gonads (testis and ovaries)
Estrogens
Progestins/progestagens
Androgens

13. Eicosanoids Metabolites of 12-C fatty acid Prostaglandins
Arachidonic acid
Prostaglandins
Produced by numerous tissues and organs
Originally isolated from prostate gland secretion
Inflammatory reaction
Reproduction
Thromboxanes, leukotriens, and prostacyclins

15. Protein hormones Short chain of amino acids Neurohormones GnRH (10)
Oxytocin (9)
TRH (3)

17. Protein hormones Large polypeptides Linear chain Subunits
Linked by disulfide bridge(s)
3-D structure
Critical for interaction with receptor

19. Chemical modification
Glycosylation
Common in gonadotropins (LH, FSH, hCG, eCG)
Sulfation
Acetylation

21. Protein hormones Isoform and variants Amino acid substitution
Gene duplication

22. Amino acid metabolites
Tyrosine metabolites
Thyroid hormones
Thyroxine
Triiodothyronine
Adrenal medulla
Epinephrine
Norepinephrine
Dopamine
Often used as neurotransmitters

24. Endocrine glands Composition Permanent or transient
Parenchyma (mass of cells)
Secretory cells
Blood vessels
Highly vasucualized
No ducts
Permanent or transient
Pituitary, adrenal, pancreas etc
Ovarian follicle and corpus luteum

25. Cells that produce hormone
Specialized secretory cells
Usually one type of cells produce one hormone
Neurons
Hypothalamus
Posterior pituitary
Adrenal medulla

26. Hormone synthesis Protein hormones Transcription Translation
Physical/chemical modification
Cleaving of long amino acid chain (preprohormones) to generate small peptide hormones (GnRH, oxytocin, TRH)
Interaction and linking of subunits
3-D structure

27. Metabolism Cholesterol (steroids) Tyrosine Smooth ER Mitochondria
Thyroid follicular cells (thyroid hormones)
Thyroglobulin
Adrenal medulla
Nerve terminals

28. Control of synthesis and secretion
Neural inputs
Brain
Hypothalamus
Hormonal stimulation/inhibition
Releasing factors/hormones
Inhibitory factors
Feedback system
Metabolic status
Stress
Blood concentrations of substances Ca
Glucose
Water

29. Hormones in circulation
Peptides and some protein hormones (i.e. insulin)
Very short half-life
Degraded by proteolytic enzymes
Large protein hormones
Longer half-life

30. Steroids Thyroid hormones Water-insoluble
Bound to binding globulins (SHBG or CBG) and albumin
Some steroids exist as free form
Short half-life
Thyroid hormones
Thyroxine-binding globulin (TBG)
Transthyretin