Download MBBS Hormone 2 Lecture PPT

HORMONES

o Term hormone was introduced by Starling and

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Bayliss in 1905.

o Hormones are the chemical messengers produced by

endocrine gland and transported by blood to other

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tissue or organ where these stimulate a change in

some metabolic activity.

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o They are produced from by one type of cell and have

regulatory effect on the activities of other type of cell

or on itself.

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o The tissue or organ stimulated by a specific hormone

are called Target Tissue/ Target organ

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o .

Hormones act on specific cells and organs called

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target cell or target organ.

o Target cell or organ is that cell which has specific

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receptors for the hormone which bind to them

with or without any demonstratable biochemical

or physiological response

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o Concentration of hormone is very low in blood

but..

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o Presence of receptors on target tissue
Specific binding between hormone and receptor
Very high local concentration
o Makes the target tissue highly specific to

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hormones

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The "information pathway". Information flows from the gene to the
primary transcript to mRNA to protein.
Hormones can affect any of the steps involved and can affect the rates
of processing, degradation or modification of the various products

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CLASSIFICATION OF HORMONES BY

MECHANISM OF ACTION

I. Hormones that bind to intracellular receptors

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1. Androgens
2. Calcitriol (1,25[OH]2-D3)
3. Estrogens
4. Glucocorticoids

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5. Mineralocorticoids
6. Progestins
7. Retinoic acid
8. Thyroid hormones (T3 and T4)
II. HORMONES THAT BIND TO CELL SURFACE

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RECEPTOR

A. The second messenger is cAMP
? 2-Adrenergic catecholamines

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? -Adrenergic catecholamines
? Adrenocorticotropic hormone (ACTH)
? Antidiuretic hormone (vasopressin)
? Calcitonin
? Human Chorionic gonadotropin, (HCG)

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? Corticotropin-releasing hormone
? Follicle-stimulating hormone (FSH)
? Glucagon
? Luteinizing hormone (LH)
? Melanocyte-stimulating hormone (MSH)

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? Parathyroid hormone (PTH)
? Somatostatin
? Thyroid-stimulating hormone (TSH
B. The second messenger is cGMP

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? Atrial natriuretic factor
? Nitric oxide
C. The second messenger is calcium or

phosphatidylinositols (or both)

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? Acetylcholine (muscarinic)
? 1-Adrenergic catecholamines
? Angiotensin II
? Antidiuretic hormone (vasopressin)
? Cholecystokinin

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? Gastrin
? Gonadotropin-releasing hormone
? Oxytocin
? Thyrotropin-releasing hormone (TRH
D. The second messenger is a kinase or phosphatase

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cascade

? Adiponectin
? Chorionic somatomammotropin

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? Epidermal growth factor (EGF)
? Erythropoietin (EPO)
? Fibroblast growth factor (FGF)
? Growth hormone (GH)
? Insulin

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? Insulin-like growth factors I and II
? Leptin
? Nerve growth factor (NGF)
? Platelet-derived growth factor
? Prolactin

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HORMONES

STIMULUS

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PROPERTY

GROUP I

GROUPII

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1.HORMONES

Adrenal steroids, thyroid Hypothalamic

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hormones,

hormones, sex hormones, pituitary

hormones,

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calcitriol ,retinoids

pancreatic

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hormones,

Adrenal hormones

2.Chemical nature

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Steroids,

iodothyronines, Peptides & polypeptides,

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retinoids

proteins,

glycoproteins,

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Catecholamines

3.Solubility

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Hydrophobic,

Water Hydrophilic Water soluble

insoluble

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4.Transport Protein

Required

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Not required

5.Receptors location

Cytoplasm and nucleus

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Cell membrane

6.Mediators of action

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Hormone

-Receptors cAMP

Complex

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cGMP
Ca ++
Phosphoinositides,

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kinase Cascade etc.


ACTION OF GROUP I HORMONES

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MECHANISM OF GROUP I HORMONE

ACTION

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The DNA Sequences of Several Hormone Response Elements

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Another member of the steroid receptor superfamily, the retinoid X
receptor (RXR), forms heterodimers with VDR, TR, and RARE, and
these constitute the functional forms of these transacting factors.
cAMP affects gene transcription through the CRE