Hormone:- organic substance secreted by organism that functions in the regulation of physiological activities and in maintaining homeostasis  Hormones are molecules that are produced by endocrine glands, including the hypothalamus, pituitary gland, adrenal glands, gonads, (i.e., testes and ovaries), thyroid gland, parathyroid glands, and pancreas The term “endocrine” implies that in response to specific stimuli, the products of those glands are released into the bloodstream.  The hormones then are carried via the blood to their target cells.  Some hormones have only a few specific target cells, whereas other hormones affect numerous cell types throughout the body.  The target cells for each hormone are characterized by the presence of certain docking molecules (i.e., receptors) for the hormone that are located either on the cell surface or inside the cell  Hormones carry out their functions by evoking responses from specific organs 7 Hormone  The interaction between the hormone and its receptor triggers a cascade of biochemical reactions in the target cell that eventually modify the cell’s function or activity.  A plethora of hormones regulate many of the body’s functions, including growth and development, metabolism, electrolyte balances, and reproduction.  Numerous glands throughout the body produce hormones. I. The hypothalamus produces several releasing and inhibiting hormones that act on the pituitary gland. II. The pituitary gland produces the pituitary hormones in response to hypothalamus signal  the hormone produced from pituitary gland act on either of other glands throughout the body or targets organs III. Other hormone-producing glands throughout the body include:-  the adrenal glands, which primarily produce cortisol; the gonads (i.e., ovaries and testes), which produce sex hormones; the thyroid, which produces thyroid hormone; the parathyroid, which produces parathyroid hormone; and the pancreas, which produces insulin and glucagon.  Many of these hormones are part of regulatory hormonal cascades involving a hypothalamic hormone, one or more pituitary hormones, and one or more target gland hormones.

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By :
Abebe Dukessa (BSc in Public Health, MSc in Medical Biochemistry, Ph.D. fellow)

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3. Objective
 At the end of this session students will be able:-
 Define Hormone
 List endocrine Glands
 Describe Function of Hormone
 Know first messenger and second messenger
 Discuss the classification of Hormone
 Explain mechanism of action of hormone
 Elaborate regulation of hormone secretion
 List Clearance of hormones
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5.  Different body part of the organism communicate each other to respond to any
changes
 Two systems help ensure communication: the nervous system and the
hormonal (i.e., neuroendocrine) system.
 The nervous system generally allows rapid transmission of information
 Hormonal communication, which relies on the production and release of
hormones from various glands into the bloodstream to transported different
body regions,
 is better suited for situations that require more widespread and longer
lasting regulatory actions.
Hormone
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6.  Thus, the two communication systems complement each other.
 Hormone:- organic substance secreted by organism that functions in the
regulation of physiological activities and in maintaining homeostasis
 Hormones are molecules that are produced by endocrine glands, including the
hypothalamus, pituitary gland, adrenal glands, gonads, (i.e., testes and ovaries),
thyroid gland, parathyroid glands, and pancreas
Hormone
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7.  The term “endocrine” implies that in response to specific stimuli, the products of
those glands are released into the bloodstream.
 The hormones then are carried via the blood to their target cells.
 Some hormones have only a few specific target cells, whereas other hormones
affect numerous cell types throughout the body.
 The target cells for each hormone are characterized by the presence of certain
docking molecules (i.e., receptors) for the hormone that are located either on the
cell surface or inside the cell
 Hormones carry out their functions by evoking responses from specific organs
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Hormone

8.  The interaction between the hormone and its receptor triggers a cascade of
biochemical reactions in the target cell that eventually modify the cell’s function
or activity.
 A plethora of hormones regulate many of the body’s functions, including growth
and development, metabolism, electrolyte balances, and reproduction.
 Numerous glands throughout the body produce hormones.
I. The hypothalamus produces several releasing and inhibiting hormones
that act on the pituitary gland.
II. The pituitary gland produces the pituitary hormones in response to
hypothalamus signal
 the hormone produced from pituitary gland act on either of other glands
throughout the body or targets organs
Hormone
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9. III. Other hormone-producing glands throughout the body include:-
 the adrenal glands, which primarily produce cortisol;
the gonads (i.e., ovaries and testes), which produce sex hormones;
the thyroid, which produces thyroid hormone;
the parathyroid, which produces parathyroid hormone; and
the pancreas, which produces insulin and glucagon.
 Many of these hormones are part of regulatory hormonal cascades involving a
hypothalamic hormone, one or more pituitary hormones, and one or more
target gland hormones.
Hormone
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14. Classification of Hormone
 Classification of Hormone according to chemical nature
1. Proteins( Peptides Hormone & Proteins Hormone)
2. Amino acid derived (Amine Hormone)
3. Steroids (Lipid soluble Hormone)
 Classification of Hormone according to mechanism of action
1. Hormones which bind to intracellular receptors(Group-II)
2. Hormones, which bind to membrane receptors(Group-I)
Water soluble Hormone
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15. 1. PROTEIN HORMONES:
I. Large polypeptides: e.g. insulin and parathyroid hormone
II. Small polypeptides: e.g. antidiuretic hormone (ADH (9aa)), oxytocin (9aa)
III.Glycoprotein hormone: e.g. Follicles Stimulating Hormone (FSH), Luteinizing
Hormone (LH), Thyroid Stimulating Hormone (TSH), Human Chorionic
Gonadotropin (HCG)
2. Amino acids derived Hormones:
I. Thyroid hormones(T3,T4)
II. Catecholamines(epinephrine and Nor-epinephrine)
III.Melatonin is derived from tryptophan
Derived from tyrosine
Classification of Hormone
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16. 3. Steroids Hormones:
 These hormones are derived from cholesterol. e.g.
I. Glucocorticoids.
II. Mineralocorticoids.
III. Sex hormones
OH
O
testosterone
O
O
progesterone
HO
O
androsterone
HO
O
estrone
HO
OH
C CH
17-ethynylestradiol
 Synthetic substances
such as 17-
ethynylestradiol are
more potent at
suppressing ovulation
 Important as oral
contraceptives
Classification of Hormone
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17. Group II. Hormones bind to
intracellular receptors
Group I. Hormones bind to cell
membrane receptors
LIPOPHYLIC (are poorly soluble in
water)
HYDROPHILIC (The water soluble
hormone)
NEED TRANSPORT PROTEINS
TO REACH TARGET TISSUES
DO NOT NEED TRANSPORT PROTEIN
LONG PLASMA HALF-LIFE
(HOURS TO DAYS).
SHORT PLASMA HALF-LIFE (MINUTES).
ACTION IS MEDIATED BY
FORMING HORMONERECEPTOR
COMPLEX
ACTION IS MEDIATED BY SECOND
MESSENGER.
INCLUDE: STEROID , THYROID ,
 CALCITRIOL and Vitamin D
INCLUDE: the catecholamines
(epinephrine and norepinephrine)
and peptide/protein hormones
Classification of Hormone

18. Group II. Hormones bind to
intracellular receptors e.g.:-
 Androgens ,
 calcitriol,
 estrogens ,
 glucocorticoids
 progestrins
 thyroid hormones
Group I. Hormones bind to cell membrane
receptors e.g.:-
A. Second messenger cAMP
 ACTH, ADH, hCG, CRH,FSH, LH, PTH.
B. cGMP as second messenger.
 ANF (atrial natriuretic factor)
 Nitric oxide (NO).
C. Calcium / phosphatidyl inositols as second
messenger
 GnRH, TRH, PDGF, Substance P.
D. Second messenger is a Kinase /phosphatase
cascade
 Insulin, GH, prolactin , insulin like growth
factors(IGF-1,IGF-2).
Classification of Hormone
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19. A. Second messenger cAMP.
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21. A. Second messenger cAMP
ACTH, ADH, hCG, CRH,FSH, LH, PTH.
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22. Mechanism of action of Group-I vs Group-II
1. Hormone Secreting glands Releasing Hormone into Bloodstream for
transport to target organs hormones binding to its receptors that located either
in cytoplasm or in nucleus form Hormone receptors complexes (HRC)
HRC translocated into the nucleus bind with Hormone Response Elements
(HRE) HRE binds to specific gene and initiate for gene expression( proteins
synthesized) proteins cried out wanted activities(Group-II)
2. Hormone Secreting glands Releasing Hormone into Bloodstream for
transport to target organs hormones(First messengers) binding to its receptors
on surface of plasma membranes Activated second messenger activate
others mediators finally gene expression( proteins synthesized) proteins
cried out wanted activities(Group-I)
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23. Mechanism of action of Hormone
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24. LIPID-SOLUBLE HORMONES
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25. HOW LIPID-SOLUBLE HORMONES WORK?
 Binding to specific cell receptor in the cell membrane
 form hormone-cell receptor complex, which diffuses to nucleus
 The receptor is eventually released for re-use
 The activates a specific gene to produce mRNA
 mRNA pass out into the cytoplasm and initiates protein [enzyme]
synthesis
 Enzyme catalyze biochemical process that contributed to cells/organ
function
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26. HOW LIPID-SOLUBLE HORMONES WORK?
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27. HOW LIPID-SOLUBLE HORMONES WORK?
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28. Step1: Free lipophilic hormone (hormone not bound with its plasma protein carrier)
diffuses through the plasma membrane of the target cell and binds with the receptor
which is intracellularly located inside the cytosol/or in the nucleus.
Step2. Each receptor has specific binding region with hormone and another region
with binding with DNA. Receptor alone cannot bind to DNA unless it binds to
hormone. Once the hormone is bound to receptor, the hormone receptor complex
binds to specific region of DNA known as Hormone response element(HRE).
Step3: Transcription of gene
Step4: m RNA transported out of nucleus into the cytoplasm
Step5: Translation at Ribosome
Step6: Protein/enzyme released from ribosome
Step7: protein/enzyme mediate ultimate response
HOW LIPID-SOLUBLE HORMONES WORK?
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29. HOW LIPID-SOLUBLE HORMONES WORK?
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30. WATER-SOLUBLE HORMONES
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31. HOW WATER-SOLUBLE HORMONES WORK?
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32. Pancreatic Hormone
 Pancreas is a large gland in body that secrete hormones
 it is part of two different organ system -Endocrine system -Digestive system
 Pancreatic Islet Langerhans cell has different types of cells which secretes
various hormones.
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34. Insulin
 INSULIN:-
 Source Of Secretion Secreted by B cells or the β-cells in the islets of
Langerhans of pancreas
 it is a polypeptide with 51 amino acids
 It has two amino acid chains called α and β chains, which are linked by
disulfide bridges
 The α-chain of insulin contains 21 amino acids and β-chain contains 30 amino
acids.
 The biological half-life of insulin is 5 minutes
 Basal level of insulin in plasma is 10 μU/mL
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Insulin

36.  Insulin Synthesis
 Occurs in the rough endoplasmic reticulum of β-cells in islets of Langerhans.
 It is synthesized as preproinsulin, that gives rise to proinsulin.
 Proinsulin is converted into insulin and C peptide through a series of peptic
cleavages.
 C peptide is a connecting peptide that connects α and β chains.
 At the time of secretion, C peptide is detached.
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Insulin
Proinsulin

37.  Insulin Metabolism
 Binding of insulin to insulin receptor is essential for its removal from
circulation and degradation.
 Insulin is degraded in liver and kidney by a cellular enzyme called insulin
protease or insulin-degrading enzyme.
 Actions Of Insulin
 Concerned with the regulation of carbohydrate metabolism and blood
glucose level.
 It is also concerned with the metabolism of proteins and fats
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Insulin

38.  On Carbohydrate Metabolism
 It is the only anti-diabetic hormone secreted in the body, i.e. it is the only
hormone in the body that reduces blood glucose level.
 Insulin reduces the blood glucose level by its following actions on carbohydrate
metabolism:
1. Facilitating transport and uptake of glucose by the cells
2. Increasing the peripheral utilization of glucose
3. Increasing the storage of glucose by converting it into glycogen in liver and
muscle
4. Inhibiting glycogenolysis
5. Inhibiting gluconeogenesis.
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Insulin

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Insulin

40. Thyroid Hormones
 Thyroid Hormones is secreted by the thyroid gland
 Thyroid gland produces two principal hormones
 Thyroxine (T4)
 Triiodothyronine (T3)
 Controlled by the primarily TSH (Thyroid stimulating hormone) secreted by the
ant Pituitary gland.
 Gland also secrete calcitonin (important hormone in calcium metabolism).
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regulate the metabolic rate of he body

41. How thyroid hormone secreted?
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Thyroid Hormones

43. Mechanism of thyroid hormone receptor action
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45. REGULATION OF HORMONE SECRETION
involve the secretion of
catecholamines by
adrenal medulla. POSITIVE
FEEDBACK
NEGATIVE
FEEDBACK
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46. FEEDBACK CONTROL
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49. CLEARANCE OF HORMONES
 Hormones are cleared by:
1.Metabolic destruction by tissues/ target cells.
2.Binding with the tissues
3.Excretion by liver into bile.
4.Excretion by kidneys into urine.
 Water soluble hormones(peptides and catecholamines) are degraded by
enzymes in the blood or tissues and are excreted by kidneys or liver. They have
a short half life.
 Lipid soluble hormones(steroids) are protein bound and are cleared slowly.
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