Dr. Dr Hewaida Fadel & Dr. Tarek El Sewedy
Department of Medical Laboratory Technology
Faculty of Allied Medical Sciences
Hormones , Vitamins and minerals
Structure and function
Intended Learning Outcomes
By the end of this lecture, students will learn:
1. Recognize The structure, function and classification of
hormones, Biomedical importance of hormones and
pathophysiology conditions related to disturbance in the
hormonal levels.
2. Learn major functions and diseases related with vitamins
and minerals.
Lecture Content
•
Hormone classification and types.
•
Hormone structure and functions.
•
Vitamins
•
Minerals
•
Deseases related to vitamin deficiency.
The endocrine system
• The survival of multicellular organisms depends on their
ability to adapt to a constantly changing environment.
• Intercellular communication mechanisms are necessary
requirements for this adaptation.
•
The nervous system and the endocrine system provide
this intercellular, organism-wide communication.
• The nervous system was originally viewed as providing a
fixed communication system, whereas the endocrine
system supplies hormones, which are mobile messages.
Hormones
•
The word “hormone” is derived from a Greek term that means to
arouse to activity.
•
As classically defined:
o A hormone is a substance that is synthesized in one organ and
transported by the circulatory system to act on another distant
tissue (endocrine action).
•
However, this original description is too restrictive because hormones
can act also on adjacent cells (paracrine action) and on the cell in
which they were synthesized (autocrine action) without entering the
systemic circulation
• There are about 200 types of differentiated cells in humans.
• Only a few produce hormones, but virtually all of the 75
trillion cells in a human are targets of one or more of the
over 50 known hormones.
• The presence of a specific receptor defines the target cells
for a given hormone.
• Receptors are proteins that bind specific hormones
and generate an intracellular signal.
• Hormones work by binding to receptors on or within the cell
and changing the activity of that particular cell).
General features of hormone classes
Types
Solubility
Transport proteins
Plasma Half-life
Receptor
Group I
Group II
Steroids
Polypeptides
and
proteins
Lipophilic
Hydrophilic
Yes
No
Long (hours to days)
Short (minutes)
Intracellular
Plasma membrane
Hormones classification
• Hormones can be classified according to:
1. Chemical structure.
2. Solubility properties.
3. Location of receptors.
4. Nature of the signal used to mediate hormonal action.
1. Structural Classifications
• Under this method of classification, there are four groups:
1. steroid hormones.
2. peptides derived.
3. amino acid derived.
4. fatty acid derived.
1. Steroid Hormones
• Steroid hormones are derived from cholesterol
The sex hormones (androgens, estrogens and progesterone) and hormones
produced in the adrenal glands.
Cholesterol derived Hormones
2. Amino acid derivative hormones
•
They are derived from tyrosine and tryptophan.
•
There are two types of tyrosine derived hormones:
Thyroxin T4
•
T3
1. Thyroid hormones (T3 and T4): regulates the development of organs and
metabolism
•
2. Catecholamines (Norepinephrine and epinephrine )
stress hormones. Both increase heart rate, dilate blood vessels and cause the
release of glucose during times of stress.
Tyrosin Derived hormones
Thyroxin Pathophysiology
•
Goiter (enlargement of thyroid
gland iodine deficiency).
•
Hypothyroidism;
(hypertension, slow heart
rate, sleepiness, sensitivity
to cold, dry skin).
•
Hyperthyroidism (Graves
disease); increase apetite,
rapid heart rate.
Tryptophan derived hormones
• Tryptophan is a precursor to serotonin and melatonin.
• 1. Serotonin is mostly found in our gastro-intestinal tract and
regulates movement in our intestines.
•
Serotonin is associated with mood and low levels often
result in depression.
•
Serotonin is also part of appetite and can make you sleepy.
• 2. Melatonin signal forms part of the system that regulates
the sleep-wake cycle by chemically causing drowsiness and
lowering the body temperature
3. Peptide derived hormones
• These are hormones derived from polypeptides.
They need to be activated
1. Insulin (Hetero-dimeric polypeptide)
Biological importance






Decrease blood glucose level.
Promote the entry of glucose and amino acids into cells.
Promote the utilization of glucose.
Has anabolic effect.
Stimulate protein synthesis.
Stimulate the cell replication.
Biological importance

It opposes the insulin action
• Single polypeptide chain
4. Fatty Acid derived hormones
• Hormones that are arrived from fatty acids are
called eicosanoids.
• hey are synthesized from a 20-carbon amino acid
called arachidonic acid.
• they are produced and secreted by nearly every cell in
the body instead of just one gland.
• Eicosanoids have various important roles in the body
including inflammation, blood pressure and blood
clotting.
• Prostaglandins are classified as eicosanoids.
2. Classification according to solubility
Lipid Soluble vs Water Soluble Hormones
•
Lipid soluble hormones are able to pass right through the target cell’s
membrane.
•
They work by binding to receptors inside the cell. This binding activates
certain proteins, which then binds to a portion of DNA inside the cell’s
nucleus causing genes to turn enzyme activity on or off, which alters the
activity of the target cell.
•
•
Steroid derived hormones are lipid soluble.
2. Classification according to solubility
Lipid Soluble vs Water Soluble Hormones
•
Water soluble hormones, act indirectly on target cells. Since the cell
membrane has a lipid bi-layer, it is hydrophobic, or water fearing. This simply
means that anything that is water soluble is not getting through. Unlike lipid
soluble hormones,
•
water soluble hormones have to bind to receptors on the surface of the target
cell.
•
Once the hormone is bound to the receptor, enzyme activity inside the cell is
altered. Depending on the hormone, enzyme activity is increased or
decreased.
•
Water soluble hormones include those that are derived from amino acids and
polypeptide hormones.
Vitamins & Minerals
BIOMEDICAL IMPORTANCE OF VITAMINS
A. Lipid Soluble vitamins
•
Vitamins are defined as a group of organic nutrients required in small quantities for a variety
of biochemical functions and which, generally, cannot be synthesized by the body and must
therefore be supplied in the diet.
•
However, vitamin D, which can be made in the skin after exposure to sunlight, and niacin,
which can be formed from the essential amino acid tryptophan, do not strictly conform to this
definition.
•
The lipid-soluble vitamins are apolar hydrophobic compounds that can only be absorbed
efficiently when there is normal fat absorption. They are transported in the blood, like any
other apolar lipid, in lipoproteins or attached to specific binding proteins.
•
Lipid-soluble Vitamins have diverse functions:
•
vitamin A, vision;
•
vitamin D, calcium and phosphate metabolism;
•
vitamin E, antioxidant;
•
vitamin K, blood clotting.
Biological importance of lipid-soluble vitamins
• dietary inadequacy or conditions affecting the digestion and
absorption of the lipid-soluble vitamins can all lead to deficiency
syndromes, including:
•
Night blindness and xerophthalmia (vitamin A);
•
Rickets in young children and osteomalacia in adults (vitamin D);
• Neurologic disorders and anemia of the newborn (vitamin E);
• Hemorrhage of the newborn (vitamin K).
• Vitamin A as well as vitamin E, are antioxidants and have possible
roles in atherosclerosis and cancer prevention.
•
Toxicity can result from excessive intake of vitamins A and D.
B. Water-Soluble vitamins
•
Water-soluble vitamins comprise the B complex and vitamin C and function as
enzyme cofactors.
•
Folic acid acts as a carrier of one-carbon units.
•
Deficiency of a single vitamin of the B complex is rare, since poor diets are most
often associated with multiple deficiency states. Nevertheless, specific syndromes
are characteristic of deficiencies of individual vitamins:
1.
Beriberi (thiamin);
2.
Glossitis (riboflavin);
3.
Pellagra (niacin);
4.
Peripheral neuritis (pyridoxine);
5.
Megaloblastic anemia and pernicious anemia (vitamin B12);
6.
Megaloblastic anemia (folic acid).
7.
Vitamin C deficiency leads to scurvy
Night Blindness
and
Xerophthalmia (Retinol Vit A)
Rickets (Vit D)
Beriberi
(Thiamin , B1)
Pellagra (Niacin)
Anemia (Vit B, Folic acid and B12)
Dermatitis
(Biotin Vit H)
Scurvy (Ascorbic Acid, Vit C)
Inorganic Minerals
• Inorganic minerals must be provided in the diet. When the intake is
insufficient, deficiency symptoms may arise, eg, anemia (iron), goiter
(iodine).
•
If present in excess as with selenium, toxicity symptoms may occur.
• For any nutrient, particularly minerals and vitamins, there is a range of
intakes between that which is clearly inadequate, leading to clinical
deficiency disease, and that which is so much in excess of the body’s
metabolic capacity that there may be signs of toxicity.
•
Between these two extremes is a level of intake that is adequate for
normal health and the maintenance of metabolic integrity.
Assignments
• Any student who did not deliver an assignment should
deliver an assignment on the “Physiological
importance of vitamins” before 24 /12/2013 or will not
be accepted anymore.
*
* Write the actions of insulin and glucagon.
* Mention the difference between Water soluble and insoluble
hormones.
*
Principles of Biochemistry, Donald J. Voet, Judith
G. Voet, Charlotte W. pratt; Willey, 3rd ed.