The endocrine system consists of glands that secrete hormones directly into the bloodstream to regulate bodily functions. Key glands include the pituitary, thyroid, parathyroid, adrenals, pancreas and gonads. Hormones control processes like metabolism, growth, development, reproduction and mood. The hypothalamus and pituitary gland work together to control hormone release from other glands and maintain homeostasis.

1. Endocrine system

2. Introduction
• Endocrine system a control system of ductless glands that secrete hormones.
• There are 2 types of hormones:
• Steroidal &
• Non-steroidal
• The multiple hormone systems play a key role in regulating almost all body
functions, including:
• Homeostasis
• Metabolism,
• Growth & development,
• Water & electrolyte balance,
• Reproduction &
• Behaviour.
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3. Cellular communications
• The human body has several means of transmitting information between cells.

4. Nerves and endocrine system
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5. Types of Glands
1. Exocrine Glands
• Release their secretions through a
duct.
• These include :
• Sweat glands
• Salivary glands
• Pancreatic glands
• Mammary glands
Endocrine Glands
• Glands which have no duct.
• Release their secretions into the
ECF or into the blood.
• This include:
• Pituitary (AP & PP)
• Thyroid, Parathyroid
• Adrenal (cortex & medulla)
• Pancreas & Gonads
• Endocrine system consists
of gland, hormone,
transport, receptor, and
target cells.
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6. Chemical classification of Hormones
1. Amines
• Hormones that are derived
from tyrosine.
• T4 & T3
• AD, NA
2. Peptides /proteins
• Hormones that are chains of
</>100 amino acids.
• ADH, Oxytocin,
• Insulin & human
growth hormone (GH).
3. Steroids
- Hormones that are lipids (cholesterol)
• Adrenal cortex (cortical
steroids)
• Gonads (sex steroids)
4. Eicosanoids
- Hormones that are lipids (FA).
• Prostaglandins
• Prostacyclins
• Thromboxanes
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7. Hormone receptor and MoA
• Events developed after
complex formation are
changes on:
• Ion channel.
• Enzymatic activities.
• G protein & 2nd
messengers.
• Gene expression &
protein synthesis.
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8. Hormone secretion control
• Hormone secretions are controlled by 4 methods:
1. Negative feedback mechanism (most hormones)
2. Positive feedback mechanism (LH- surge)
3. Neural control
• Secretion of OT, ADH, AD, NA
4. Circadian rhythm (periodic variations)
• Secretion of Sex hormones
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9. Hypothalamus
• Is part of the diencephalon &about 5
gm.
• It plays most important role in
controlling homeostasis.
• It is the main brain structure
involved in regulating hormonal
levels in the body.
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10. Hypothalamic hormone Effect on pituitary
Corticotropin releasing hormone
(CRH)
Stimulates ACTH secretion
Thyrotropin releasing hormone (TRH) Stimulates TSH and Prolactin
secretion
Growth hormone releasing
hormone (GHRH)
Stimulates GH secretion
Somatostatin (GHIH) Inhibits GH secretion
Gonadotropin releasing hormone
(GnRH)
Stimulates LH and FSH secretion
Prolactin releasing hormone (PRH) Stimulates PRL secretion
Prolactin inhibiting hormone
(dopamine)
Inhibits PRL secretion
Hypothalamic releasing/inhibiting hormones
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11. APG and PPG
ADH (vasopressin)
• Regulate body water &
BP by reabsorption of
water & vasoconstriction
of arteries and arterioles
• Oxytocin: contract
endometrial & breast
SM.
• Secretion from the gland
controlled by nerve signals.
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• The AP lobe receives
hormones (RH & IH) from
the HT.
• No nerve fibers are
terminated in to APG.
• Secretion process is
regulated by blood born
hormones.

12. Hormones of anterior & posterior pituitary glands
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13. Growth hormones
• Promotes tissue growth by stimulating liver to
produce IGF-I/Somatomedin-C
• Promote protein synthesis
• Increase DNA transcription
• Increase mRNA production
• Enhance amino acids into cell & reduce protein
catabolism.
• Increase protein sparing, not used as energy.
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14. Thyroid gland
• The largest endocrine gland
in the body.
• Positioned on the neck just
below the Larynx & has 2
lobes with one on either side
of the trachea.
• It produce hormones T3
(triiodothyronine) & T4
(thyroxine).
• T3 & T4 increase the
metabolic activity of the
body’s cells.
Function of the thyroid hormones
1. Calorigenic action
 ↑O2 consumption
 ↑Metabolic rate on CHO,
protein and Fat
 Body growth: promotes
growth of bone, teeth and nerve
tissue in children
3. Effect on NS/CNS
 Promotes growth and maturation
of nerve tissue, synaptic
development.
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15. Calcitonin
• A hormone that is produced by the parafollicular cells (C-cells) of
the thyroid.
• Produced by the thyroid & contributes to the regulation of blood
ca+2 levels.
• Thyroid cells produce calcitonin in response to high ca+2 levels in
the blood:
• Decreases the concentration of ca+2 in the blood.
• This hormone will stimulate movement of calcium into the bone
structure.
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16. Parathyroid gland
• Are 4 glands located on the
thyroid gland having
butterfly-shaped.
• Functions: Regulate the
body's calcium &
phosphorus levels.
• Secrete PTH [parathyroid
hormone], which
• Causes release of ca+2 from
bone to ECF.
• ↓ Osteoblasts (production
of bone) &
• ↑ Osteoclasts (removal of
bone).
• Signals the kidneys to
reabsorb ca+2 .
• Signals the small intestine to
absorb more ca+2
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17. Summary of Ca-homeostasis
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18. Adrenal glands
• Triangular-shaped glands located on
top of the kidneys.
• They regulate many essential
functions in the body, including:
– biochemical balances that
influence:
• Athletic training &
• General stress response.
• Produce hormones like:
– Aldosteron
– Cortisol
– Androgens
• Produces chemicals like:
– AD, NA
– Dopamine
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19. Adrenal Cortex
1. Mineralocorticoids
(Aldosterone)
– regulate the salt & water
balance, leading to the increase
of BV & BP.
2. Glucocorticoids (Cortisol)
– raise blood glucose level,
stimulates breakdown of
protein.
3. Sex Hormones (Androgen)
– stimulates reproductive organs
& brings on sex characteristics.
Adrenal Medulla
• The effects of these hormones
provide a short-term
response to stress.
• Impulses from HT, spinal cord &
SNS fibers go to the adrenal
medulla,
• Then it releases hormones:
– Epinephrine
– Norepinephrine
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Adrenal glands

20. Pancreas
• It is both an exocrine & an
endocrine organ.
• As an exocrine organ; it is
considered to be part of the
GIT.
• It produces digestive enzymes
to be released into the SI.
• Aid food digestion to
absorbable.
• Endocrine function.
• Secret Insulin & glucagon
• They are secreted by islet cells
released into the bloodstream.
• Groups of endocrine cells
(Islets of Langerhans) secrete
two hormones.
1. Beta cells [β]
• secrete Insulin
1. Alpha cells [∂]
• secrete Glucagon.
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21. • Insulin
• Lower blood sugar levels
by allowing the sugar to
flow into cells.
• Glucagon
• Raise blood sugar levels
by causing glucose to be
released into the
circulation from its storage
sites.
• Insulin & glucagon act in an
opposite but balanced fashion
to keep blood sugar levels
stable.
1. On Carbohydrate
• blood glucose level by:
• Converting into glycogen
• Facilitate cells uptake
• Converting to fats & stored in the
adipose tissue
2. On Protein
– Promotes amino acid uptake by cells
and inhibits proteins breakdown.
3. On Cortisol
– Anti-cortisol effect =blood glucose by:
• inhibiting gluconeogenesis &
• activating glucose uptake
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Insulin metabolic Effects