1. Hormones and their examples, characteristics

Hormones and their characteristics

1. Introduction to hormones
E. A. Tagoe
2019

2. To learn:
Basic introduction of hormone
General mechanisms of hormone action
Regulation of hormone level
Actions of specific hormones
Clinical correlations.
Hormones: Specific objectives

3. Hormonesarechemicalsubstancesreleasedby
cellsorglandsinthebodythatsendoutmessages
thataffectcellsoftheorganismORchemicalsignals
thatcoordinatethedifferentpartsofanorganism.
Theword'hormone'comesfromaGreektermthat
means'toexcite‘.
Hormonesarerequiredforcellularcommunication.
Hormones

4. Hormones: Terminologies
Signal: the chemical message
Ligand: The chemical (hormone) released to send signal.
Receptor: the structure on cells that receive the signal.
Receptor activation: When receptor respond to signal.

5. Hormonesareproducedinverysmallamountsinoneareaof
anorganismandarethensenttoanotherpart,wherea
responseistriggered.
Hormonesproduction,release,actionandterminationof
actionaretightlyregulatedbytheorganism.
Hormonesaretransportedtothesiteofactioniftargetcellis
notthesameasthatwhichproduceditoradjacentcells.
Allhormoneshavespecifictargetorreceptor.
Hormones: General characteristics

6. Hormones:Cells stimulation and release of hormones
Cells and glands produce and release hormones after a
hormonal stimulation.

7. Hormones: Hormones to targeted cells

8. Hormones: Autocrine and paracrine signaling

9. Hormones: Endocrine mediation

10. Hormones: Exocrine mediation

11. Hormones: Neurocrine

12. Hormones: Neurocrine

13. Chemically,hormonesareoffourtypes:
Hormonalamine
Steroids
Peptide,proteinorglycoprotein
Hormones: Classification of hormones

14. Hormones: Hormonal amines
1. Hormonal amines: are derived from the amino acids
(eg: tyrosine) and secreted by glands.
Examples of glands that secret hormonal amines
Adrenal medullar
Thyroid gland
Pineal gland in the brain

15. Hormones: Characteristics of hormonal amines
•Stored until secreted
•Receptor locations:
-Surface
-Intracellular

16. Hormones: Hormonal amines

17. Hormones: Steroid Hormones

18. Hormones: Steroid Hormones

19. Hormones: General characteristics of steroid Hormones
•They are secreted by three “steroid glands”—the adrenal
cortex, testes, and ovaries.
•Steroid hormones are lipophilic.
•Can pass through cell membrane into the cell.
•Bind cytoplasmic or nuclear receptors
•Usually activate DNA for protein synthesis

20. •Control metabolism
•Inflammation
•Immune functions
•Salt and water balance
•Development of sexual characteristics
•Ability to withstand illness and injury.
Hormones: General functions of steroid Hormones

21. Hormones
3. Peptide, Protein, and Glycoprotein Hormones
Peptide hormones:-are composed of polypeptide chains with a
size ranging from three to hundreds of amino acids.
Most peptide hormones are water soluble and therefore do not
require carrier proteins to circulate in the blood stream.
The peptide solubility results in rapid hormone degradation by
plasma proteases.
The hormones have shorter half-life and duration of action
compared to other types of hormones, such as steroid and thyroid
hormones.

22. Hormones
3. Peptide, Protein, and Glycoprotein Hormones
Proteins and glycoprotein hormones:-just like the peptide
hormones.
The proteins cannot go through the cell and nuclear membranes
They are globular

23. Summary of the Different Classes of Hormones

24. Hormones : Mechanisms of hormone actions
The different types of hormones have different mechanisms of action
due to their distinct chemical properties.
Steroid Hormones
Steroid hormones are lipophilic (fat-loving) –freely diffuse across the
plasma membrane of a cell
•They bind to receptors in either the cytoplasm or nucleus of the
target cell, to form an active receptor-hormone complex.
•Activated complex move into the nucleus and bind directly to DNA,
acting as a transcription factor for gene expression.

25. Hormones : Mechanism of hormone actions
Steroid hormones freely diffuse through the cell membrane to
complex with the receptor in the cytoplasm.

26. Peptide Hormones
•Peptide hormones are hydrophylicand lipophobic(fat-hating) –cannot
freely cross the plasma membrane.
•Peptide hormones bind to receptors on the surface of the cell. The
receptors are typically coupled to internally anchored proteins (e.g. G
proteins)
•The receptor complex activates a series of intracellular molecules called
second messengers, which initiate cell activity.
Hormones : Mechanisms of hormone actions

27. Hormones : Mechanisms of hormone actions
•Production of second messengers is called signal transduction, because
the external signal (hormone) is transduced via internal intermediaries.
•Examples of second messengers include cyclic AMP (cAMP), calcium
ions (Ca
2+
), nitric oxide (NO) and protein kinases
•The use of second messengers enables the amplification of the initial
signal (as more molecules are activated).
•Hormones include insulin, glucagon, leptin, ADH and oxytocin

28. Hormones : Mechanisms of hormone actions
Initialsignalingmolecule(peptidehormone)bindstosurfacereceptor,
andanchoredproteinrelaytheinformation(signal)downstream
throughsecondmessengersuntilthesignalreachesnucleus.

29. Amine hormones do not all share identical properties and have
properties common to both peptide and steroid hormones
Hormones : Mechanisms of hormone actions

30. Hormones : Comparison of hormone actions

31. Mechanism of hormone action
Activation/inactivation of an
enzyme; opening/closing a
membrane channel;
activating a transcription
factor

32. Mechanism of hormone action

33. How is the signal from
the hormone (signal
molecule) binding to the
receptor transmitted
into the interior of the
cell?
Mechanism of hormone action

34. Insulin hormone
Insulin is a peptide hormone produced by beta cells of the
pancreas.
It functions to regulate carbohydrate and fat metabolism.
Main function is to promote glucose absorption in the liver,
muscle and fat cells from the blood.
Low or nonfunctional insulin or its receptors have been
implicated in increased blood sugar levels (Diabetes
mellitus).

36. •Insulin works through a
tyrosine kinase (TK)
receptor mechanism
•Binding of insulin to the
extracellular domain of
the tyrosine kinase
leads to activation and
phosphorylation of
downstream protein
Insulin from Beta cells of the pancreas
Mechanism of insulin action

37. Mechanism of insulin action

38. Insulin-mediated glucose transport signaling pathway
Insulin
IR
a
b
b
a
P
IRS
PI3K
Akt
P
Glut4
glucose
Extracellular
domain
Intracellular
domain

39. Insulin
P
IRS
PI3K
Akt
P
IR
aa
b
b
glucose
Extracellular
domain
Intracellular
domain
glucoseanti-lipolysisglycogen protein cell
transport synthesissynthesisgrowth
Insulin-mediated glucose transport signaling pathway

40. Signal
amplification
What are the advantages
of having an amplified
signal?
What might be some
disadvantages of a
sustained receptor
activation?

41. Regulation of hormone level/action
Degradation of downstream moleculaes
i. Rapid hydrolysis of activating molecules bound to receptors
(eg: G protein / receptor interaction)
ii. Conversion of molecules that activates downstream enzymes
(eg: Hydrolysis via cAMPby phosphodiesteraseto
5’-AMP stops the signal)

42. Feedback hormonal control
Regulation of hormone level/action

43. •Internalization of receptors
Receptor of the hormone is internalized. Signal is then
terminated.
•Down-regulation of receptors
High insulin concentrations reduce the number of insulin
receptors
•Degradation of the hormone
Circulatory hormones are cleared by degrading enzymes
•Receptors inhibitors
Receptors of hormone are blocked with specific inhibitor
Regulation of hormone level/action

44. Clinical correlations
Discuss the following:
1.A patient was diagnosed with defective GLUT-4. State and
explain the possible clinical outcomes?
2.Leptinisacell-signalinghormonevitalintheregulationof
appetite,foodintakeandbodyweight.Absenceofleptinin
thebodyorleptinresistancecanleadtouncontrolledfeeding
andweightgain.Baseonthisinformation,whatdoyou
suggestaDieticianmustprobablyconsiderfirstinmanaging
obesity?

45. 3. Dopamine, a neurohormone serves as the major prolactin-
inhibiting factor and attenuates prolactin secretion. Dopamine is
secreted into portal blood by hypothalamic neurons, binds to
receptors on lactotrophs, and inhibits both the synthesis and
secretion of prolactin.
i.A middle age woman was diagnosed with infertility and the
condition was attributed to deficient dopamine. How does the
deficient dopamine accounted for the infertility?
ii.Suggest ways by which the woman condition can be
improved (Target the cell signaling).