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1. HERMONES AND ITS CLASSIFICATION
Presented By
Umar Ali
S/O Bakht Zaman

2. Hormones and its classification

3. What’s Hormone?
• chemical messengers that
are secreted directly into
the blood, which carries
them to organs and tissues
of the body to exert their
functions.
•
• organic substances,
produced in small amounts
by specific tissues
(endocrine glands),
secreted into the blood
stream to control the
metabolic and biological
activities in the target cells.

4. Properties of Hormones
• 1. Hormones are produced by a specialized glands and are secreted
directly into the blood stream.
• 2. Hormones are transported by the blood stream from the endocrine cells
to serve as ‘chemi­
cal messenger’ which act on target cells or organs by
regulating the rates of specific metabolic reactions.
• 3. Hormones exert their effects not where they are locally produced, but
on other tissues of the body.
• 4. Hormones are required in very small amounts and their effect may be
excitatory or inhibitory depending upon their concentration and the
physiological state of the responding tissue.
• 5. Hormones belong to different types of chemical structure. They may be
steroids, proteins, peptides or amino acid derivatives.

5. Functions
• There are many types of hormones that act on
different aspects of bodily functions and
processes. Some of these include:
• Development and growth
• Metabolism of food items
• Sexual function and reproductive growth and
health
• Cognitive (mental) function and mood
• Maintenance of body temperature and thirst

6. Classification of hormones
• Hormones can be classified according to their
• Chemical nature,
• Mechanism of action,
• Nature of action,
• Stimulation of Endocrine glands and
• Effects of hormones

7. Chemical nature of hormones
Based on the chemical nature the hormones can be categorized into three groups
Protein or peptide hormones e.g. insulin, glucagon,
antidiuretic hormone, oxytocin.
Steroid hormones e.g. glucocorticoids, mineralocorticoids,
sex hormones.
Amino acid derivatives e.g. epinephrine, norepinephrine,
thyroxine (T4), triiodothyronine (T3).
But more specifically it is divided into six classes, they are hormones
steroid; amines; peptide; protein; glycoprotein and eicosanoid.

9. Mechanism of action of hormones
Group I Hormones Group II Hormones

10. Group I hormones
• Includes group of lipophilic hormones that are usually derived from
cholesterol (except T3 and T4).
• Steroid hormones are lipophilic (fat­
loving) – meaning they can freely
diffuse across the plasma membrane of a cell.
• bind to receptors in either the cytoplasm or nucleus of the target cell, to
form an active receptor­
hormone complex
• This activated complex will move into the nucleus and bind directly to
DNA, acting as a transcription factor for gene expression.
• DNA mRNA protein causes
biochemical changes in the cell.
• Examples of steroid hormones include those produced by the gonads (i.e.
estrogen, progesterone and testosterone)

11. Group I hormones

12. Group I Hormones

13. Group II hormones
• Include peptide hormones
• are hydrophylic and lipophobic (fat­
hating) – meaning they cannot freely cross the
plasma membrane
• They bind to receptors on the surface of the cell, which 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
• This process is called signal transduction, because the external signal (hormone) is
transduced via internal intermediaries
• Examples of second messengers include cyclic AMP (cAMP), calcium ions (Ca2+),
nitric oxide (NO) and protein kinases
• The use of second messengers enables the amplification of the initial signal (as
more molecules are activated)
• Peptide hormones include insulin, glucagon, leptin, ADH and oxytocin

14. These are hormones that bind to cell surface (plasma membrane) receptor
enter into the cell then stimulate the release of certain molecules known as second
messenger which will then perform the biochemical function of these hormones.
cAMP act as secondary messenger.
activates (Protein Kinase) various enzymatic reaction to cause biochemical changes.
After the target cell responded to the changes, cAMP is deactivated by a group of
enzyme Phosphodiesterase

15. Group II hormones

16. Group II hormones

17. Nature of hormones action
• a. Local hormones—
These hormones have a
specific local effect
through paracrine
secretion, for example,
hormone testosterone
• b. General hormones—
These are hormones
transported through
circulation to the distal
target tissue/organ
examples are thyroid
hormones and insulin

18. Stimulation of Endocrine glands
• a. Tropic hormones—
• hormones that stimulate other
endocrine gland for secretion
examples are TSH which stimulate
secretion of thyroid gland for the
production of thyroid hormones
• b. Nontropic hormone—
• hormones that usually exert their effect
on non-endocrine target tissues examples
of these hormone are Thyroid hormone
which increases the rate of oxygen
consumption and metabolic activity of
different cells in the body.

21. Effect of hormones
• a. Kinetic hormones—
• These hormones may cause muscle contraction, pigment
migration, glandular secretion and others, example of these
hormones is epinephrine
• b. Metabolic hormones—
• These are hormones that mainly caused changes in the
rate of metabolism and balance the reaction examples
include insulin, glucagon, parathyroid hormones.
• c. Morphogenetic hormones—
• These are hormones that mainly involved in growth and
differentiation in the body, examples are Follicle
stimulation hormones, luitenizing hormones and thyroid
hormones

22. Any Queries?