Endocrine Physiology

For Optometry
Students
2011 E.C

BY ; Mengistu D
University of Gondar
 Objectives
At the end of this chapter the student will be able to:
1. Explain the endocrine system and its functions
2. Mention chemical classes and solubility properties of
hormones
3. Identify major endocrine glands and their hormones
4. Describe major functions of each hormones
5. List the endocrine disorders

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 Outlines
• Introduction
• Coordination systems
• Function of the endocrine system
• Components of the endocrine system
• Hormones: type, classification, control…
• Endocrine glands & hormones
• Endocrine disorders

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 Introduction
• Endocrine system = a control system of ductless glands
that secrete hormones within specific organs.
"messengers“ carried by the bloodstream to different
cells in the body.
 maintain homeostasis & respond to stimuli is largely
due to hormones.
• Endocrine system provides an electrochemical connection
from the hypothalamus of the brain to control almost all
body functions.
• The endocrine system regulates its hormones through
negative feedback, except in very specific cases like
childbirth.
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 Coordination systems
Nervous System Endocrine System
• Rapid response. • Slow response.
• Short lasting effect. • Long lasting effect.
• Uses neurotransmitters • Uses hormones

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 Functions of the endocrine system
1. Homeostasis:
 Maintenance of the internal environment at the optimum
biochemical environment:
– Regulates ABP:AD,NAD, Ang-II, ANP, NO
– Thermoregulation: AD, NAD, T3/T4
– Mass change (bone, muscle, fat) GH, androgens
– Immunoregulatory function: cortisol
– Regulates RBC formation: EPO, GH, T3/T4,
testosterone
– Ca2+ homeostasis: PTH, calcitonin
– Glucose homeostasis: insulin, glucagon

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 Functions of the endocrine system…
2. Regulation of Reproduction:
– gametogenesis
– sexual desire
– fertilization
– fetal growth & development
– nourishment of the newborn
3. Regulation of Body Growth & Development.
4. Production, utilization and storage of Energy.

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 Components of endocrine system
1. Glands
hypothalamus, pineal gland, pituitary, thyroid,
parathyroid, thymus, pancreas, adrenal gland & gonads.
2. Hormones
 t3 t4 , oxytocin, ADH, ACTH, FSH, LH, GH, insulin,
glucagon, aldosterone, testosterone, estrogen,
3. Transport media [blood & ECF].
4. Receptors
5. Target tissue [cells/organs].

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 Types Glands
1. Exocrine Glands
• Release their cellular secretions through a duct which
empties to the outside or into the lumen (empty internal
space) of an organ.
• These include :
–Sweat glands
–Salivary glands
–Pancreatic glands
–Mammary glands

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 Types Glands …
2. Endocrine Glands
• Glands which have no duct & release their secretions
directly into the extracellular fluid or into the blood.
–Their collection makes up the endocrine system.
• This include:
–Pituitary (anterior & posterior lobes)
–Thyroid, Parathyroid
–Adrenal (cortex & medulla)
–Pancreas & Gonads

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 Hormones
• A specific chemical compound released in one part of the
body and act some other parts.
• Made in glands or other cells.
• Transported by blood.
• Transmit signal from one cell to other.
• Cause cell responses.

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• Most hormones circulate in blood, coming into contact with
essentially all cells.
– a given hormone usually affects only a limited number
of cells, which are called target cells.
• A target cell responds to a hormone because it bears
receptors for the hormone.

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 Chemical classification of Hormones
1. Amines: hormones that are derived from tyrosine.
- T4 & T3 (thyroid hormones)
- Epinephrine, Norepinephrine
2. Peptides /proteins: hormones that are chains of AA
– ADH, Oxytocin, Insulin, GH,TSH, FSH and LH
– most abundant type
3. Steroids
- Hormones that are lipids synthesized from cholesterol
• Adrenal cortex (cortical steroids), Gonads (sex
steroids), Vit-D3
4. Eicosanoids: hormones that are lipids synthesized from
fatty acid.
• Prostaglandins, Prostacyclins, Thromboxanes 13
 Classes of hormones based on solubility
Water soluble (Hydrophilic Lipid soluble (Lipophilic
hormones) hormones)
 Catecholamines  Thyroid hormone
– Epinephrine – T4 & T3
– Norepinephrine  Steroid hormones
Peptide/Protein hormones – Aldosterone
– ADH & Oxytocin – Testosterone
– GH & Insulin – Vitamin D3

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 Hormone:
synthesis, storage, release & transport
 Site of synthesis:
– Protein/peptide hormones: in the RER
– Steroid hormones: in the SER
 Storage:
– Protein/peptide hormones: preprohormones in
vesicles
– Steroid hormones: cholesterol
 Release:
– Exocytosis
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 Hormone: synthesis, storage...
 Transport:
• Hormones are transported in blood in two forms:
– free form
– combined with plasma proteins (albumin & globulin)
 Metabolism:
 metabolized in the liver or by target cells.
 Excretion:
 urine, feces, sweat.

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 Hormone transport in the blood
 In two ways
1. Freely by the blood:
– Peptide hormones
– Catecholamine
2. Binding on plasma
proteins:
– Cortical steroid
– Gonadal hormones

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 Hormone Receptors and Mechanisms of
Action
• Hormone reach into the target tissue by diffusion.
– Binding of specific receptors at the target cell.
• Based on hormones solubility, receptors are found:
1. On the cell membrane
 Peptide hormones
 Catecholamine
2. Inside the cell
 Cytoplasm = Steroid hormones
 Nucleus = Thyroid hormones
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Hormone Receptors and Mechanisms of Action

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 Effects caused by hormone

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 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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 Hormone secretion control (cont’d)

NFM
the most
common
hormonal
secretion
controlling
mechanisms.

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Endocrine glands & their respective hormones

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 1. Hypothalamus
• Is part of the diencephalon, which forms the floor & the
lateral wall of the 3rd ventricle.
• Represents less than 1% of the brain mass, about 5 gm.
– Regardless of its size, 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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 Function of Hypothalamus
1. Endocrine function: controls:
– Adenohypophyseal hormones
– Neurohypophyseal hormones
– Adrenal medulla
2. Controls the ANS
– Anterior nuclei acts as a parasympathetic center
– Posterior nuclei acts as a sympathetic center
3. Regulation of body temperature
-Heat losing center (anterior HT)
-Heat gaining center (posterior HT)
-Thermostat center (anterior preoptic)
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 Function of Hypothalamus…
4. Contributes to the regulation of:
- sleep, emotions, anger, fear, pain & pleasure.
5. Controls food intake (hunger sensation):
- Feeding center (lateral HT),
- Satiety center (ventromedial HT)
6. Control of water-electrolyte balance
- Thirst center (lateral HT )
- Osmoreceptors (anterior HT )

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 Function of Hypothalamus…
7. Control of sexual behavior: libido, sexual activities are
controlled by cerebral cortex, limbic system and HT.
8. Regulates MR
– by stimulating calorigenic hormones such as T3/T4, AD,
NA, glucocorticoids.
9. Controls
– milk letdown and
– utrine contraction.

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 Hypothalamus …
Receives nervous stimuli from receptors throughout the
body & monitors chemical & physical characteristics of the
blood, including:
T0, BP, nutrient, hormone, water content.
When deviations from homeostasis occur or when certain
developmental changes are required,
hypothalamus stimulates cellular activity in various parts
of the body by directing the release of hormones from the
anterior & posterior pituitary glands.

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Hypothalamic releasing/inhibiting hormones
Hypothalamic hormone Effect on pituitary
Corticotropin releasing hormone Stimulates ACTH secretion
(CRH)
Thyrotropin releasing hormone Stimulates TSH and Prolactin
(TRH) secretion
Growth hormone releasing hormone Stimulates GH secretion
(GHRH)
Somatostatin (GHIH) Inhibits GH secretion

Gonadotropin releasing hormone Stimulates LH and FSH secretion

(GnRH)
Prolactin releasing hormone (PRH) Stimulates PRL secretion

Prolactin inhibiting hormone Inhibits PRL secretion

(dopamine)
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Hypothalamus and Pituitary gland
Magnocellular
neurons

Parvicellular
neurons

30
 2. Pituitary gland (hypophysis)
• Below hypothalamus
• The master gland
• It is divided into two
sections:
I. Anterior lobe/pituitary
 Adenohypophysis
 True gland
II. Posterior lobe/pituitary
 Neurohypophysis
 Not true gland

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 I. Posterior pituitary gland
• Hormones produced by the cell bodies of the
neurosecretory cells are:
 packaged in vesicles & transported through the
axon & stored in the axon terminals that lie in the
posterior pituitary.
• Only store hormones:
- ADH (vasopressin) :regulate body water & BP.
- Oxytocin: contract endometrial & breast smooth
muscles cells.
• Secretion from the gland controlled by nerve signals.

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 Posterior pituitary gland…
• Magnocellular neurons
in the paraventricular &
supraoptic nuclei
secrete oxytocin and
vasopressin (ADH)
directly into capillaries in
the posterior lobe

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Antidiuretic hormone (ADH), Vasopressin
Function:
• Promotes reabsorption of water in the renal tubules
• Vasoconstriction of arteries and arterioles
• Involved as a NT in memory and pain
• Regulates osmolality and volume of ECF
Factors stimulating release of ADH
• Hyperosmolality
• Change in blood volume
• An increased in Ang-II
• Drugs, pain, stress
Hypo secretion of ADH: Diabetes insipidus .

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Regulation of ADH secretion
Factors activating the SON
1. Body fluid hyperosmolality,
hypovolemia
2. Drugs: morphin, nicotine, Ach,
aspirin
3. Ang-II

Factors inhibiting the SON

1. Pressure & volume receptors
2. Drugs: PG-E, alcohol, Ad, NA
3. ANP

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 Disorders related to ADH
 Diabetes insipidus (DI)
• Characterized by excretion of large amounts of severely
diluted urine & excessive thirst.
• Caused by ↓ADH/kidney insensitivity to the hormone .
• Symptoms
– Excessive urination & extreme thirst.
• Urine is not sweet as it does not contain glucose &
• No hyperglycemia (make differ from other diabetes)

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 Oxytocin
Function
• Induces uterus contraction (Labor)
• Induces myoepithelial contraction (lactation)
• Acts as PRL releasing hormone
• Facilitates ovulation, transport of sperm in both males &
females ductile system
Regulation of OT secretion
1. Tactile stimulation of the nipple (suckling)
2. Genital stimulation
3. Estrogen increases sensitivity of target cells to OT
4. Fear, pain, adrenalin and alcohol inhibit OT secretion
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 II. Anterior Pituitary Gland
Composed of glandular epithelium.
The anterior pituitary lobe receives hormones (RH & IH)
from the hypothalamus via a portal vein system known as:
– hypothalamic - hypophyseal portal system
No nerve fibers are terminated in to APG.
– Secretion process is regulated by blood born hormones.

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 Anterior pituitary hormones
Hormones Functions
GH Promotes growth and metabolism
PRL Promotes milk secretion, breast growth,
and maintains lactation
ACTH Stimulates adrenal cortex to produce
aldosterone and cortisol
TSH Stimulates the thyroid gland to secret
T3/T4
LH Promotes ovulation
Stimulates Leydig cells to testosterone
secretion
FSH Stimulates growth and maturation of ova
Stimulates secretion of oestrogen
Stimulates spermatogenesis
Hormones of anterior & posterior pituitary glands

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 Anterior pituitary gland…
• Parvicellular
neurosecretory cells
secrete releasing hormones
into capillaries of the
pituitary portal system at the
median eminence
 which are then transported
to the anterior pituitary
gland
to regulate the secretion of
pituitary hormones.

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Anterior pituitary cells and hormones
Cell type Pituitary Product Target
population
Corticotropes 15-20% ACTH Adrenal gland
b-lipotropin Melanocytes
Adipocytes

Thyrotropes 3-5% TSH Thyroid gland

Gonadotropes 10-15% LH, FSH Gonads
Somatotropes 40-50% GH All tissues, liver
Lactotropes 10-15% PRL Breasts
gonads

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 Growth hormone
Physiological effects of GH
• 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(deposition in tissues), not
used as energy.
• Promotion of protein Promotion of fat utilization for energy
• Impairment of CHO utilization for energy
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 Growth hormone effects
• On lipid
– Increase FA released from cell.
• On CHO
– Glucose sparing effect. (Hyperglycaemic hormone)
• On electrolytes
– Increase Na+, Cl-, K+ retention & Ca++ absorption.
• On GIT
– Increase absorption of nutrients.
• Others:
– ↑RBC formation, ↑MR, Thermogenic, ↑secretion of
Insulin & Somatomedin-C.
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Growth hormone…
 Disorders of GH secretion
A. Hyposecretion of GH B. Hypersecretion of GH
– Results in dwarfism •Gigantism
•Acromegaly

2.51m

54.6 cm
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 Adrenocorticotropic hormone (ACTH)
• Control the release of adrenocortical hormones.
– These hormones affect metabolism of:
• glucose, proteins & fat, indirectly.
• Secreted in response to CRH (corticotropic releasing
hormone) from hypothalamus.
• Has target cells on adrenal cortex, so it is specific
hormone.

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 Thyroid stimulating hormone
[TSH / Thyrotropin]
• Thyroid gland is the target tissue.
• Controls the rate of secretion of:
– Thyroxine (T4) and
– Triiodothyronine (T3)
• These hormones control the rates of most intracellular
chemical reactions.

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 Prolactin(PRL)
Function
• Promotes growth and development of breast
• Maintains lactation, delays ovulation and suppresses
fertility by inhibiting the action of LH and FSH
• Promotes milk secretion
• Enhances production of progesterone
• Enhances function of testosterone
• Promotes growth

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 Prolactin(PRL)…
PRL in males
• ↑Testosterone production, ↑Libido
• ↑ Secretion of prostate gland and seminal vesicles
HYPERPROLACTENEMIA
Excessive production of PRL
↑↑PRL suppresses gonadal function, loss of libido
Causes
1. Hypothalamic disorders
 Lesion to dopaminergic neurons
2. Pituitary disorders
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 Gonadotropic hormones
• Testes & ovaries are the target organs.
• Gonadotropic hormones are:
FSH and LH.
• Absent from the blood in prepubertal boys and girls
• Triggered by GnRH during and after puberty
• Control growth of the ovaries & testes.
Function
 LH works with FSH to cause maturation of ovarian
follicle
 LH works alone to trigger ovulation
 LH promotes synthesis and release of estrogen &
progesterone
 LH stimulates interstitial cells of testes to produce
testosterone 51
 3. 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 is involved in the production of the hormones T3
(triiodothyronine) & T4 (thyroxine).
– T3 & T4 increase the metabolic activity of the body’s
cells.
• Production of T3 & T4 are regulated by TSH, released by
the pituitary gland.
– TSH production is increased when T3 & T4 levels are too
low. 52
 Thyroid gland...
• Thyroid gland manifests a remarkably powerful active
transport mechanism for up-taking iodide ions from the
blood.
– As blood flows through the gland, iodide is converted to
an active form of iodine.
– This iodine combines with an amino acid called
tyrosine.
• 2 molecules of iodinated tyrosine then combine to form
thyroxine.
– Following its formation, thyroxine becomes bound to a
polysaccharide-protein material called
thyroglobulin/TG.
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 Thyroid gland...
 An enzymatic splitting of the thyroxine from the TG occurs
when a specific hormone (TSH) is released into the blood.
A variety of bodily defects [either dietary, hereditary, or
disease induced] may decrease the amount of thyroxine
released into the blood.
The most popular of these defects is one that results from
dietary iodine deficiency.
Thyroid gland enlarges, in the continued presence of TSH
from the pituitary to form a goiter.

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 Function of the thyroid hormones (T3 & T4)
1. Calorigenic action
 ↑O2 consumption (↑oxidative metabolism)
 ↑Metabolic rate = Thermogenic
T3/T4
 ↑Vit-A utilization: Carotinon Vit-A
2. Body growth: promotes growth of bone, teeth and nerve
tissue in children
 ↓T3/T4 = Cretinism, dwarfism plus mental retardation .
3. Effect on NS/CNS
 Promotes growth and maturation of nerve tissue
 Promote normal synaptic development
 Essential for normal function of the brain
 Causes mental alertness. Hyper secretion leads to
nervousness
55
 Function of the thyroid hormones (cont’d)
4. Metabolic function
On CHO metabolism
↑Glycogenolysis
↑Glucose utilization
↑Gluconeogenesis
↑Glucose absorption
On protein metabolism
↑Protein synthesis
↑ ↑T3/T4 = Protein catabolism
On Fat metabolism
↑Lipolysis

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Function of the thyroid hormones (cont’d)

5. Other actions of the thyroid hormones

 ↓Plasma cholesterol
 Normal gonadal function
 Lactation: ↑milk secretion
 Stimulates erythropoiesis
 Normal GIT function, appetite
 Water-electrolyte balance

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 Calcitonin
• A hormone that is produced in humans primarily by
the parafollicular cells (C-cells) of the thyroid.
– Additional hormone produced by the thyroid &
contributes to the regulation of blood ca++ levels.
• Thyroid cells produce calcitonin in response to high ca++
levels in the blood:
– Decreases the concentration of ca++ in the blood.
– Counteract the calcium-producing effects of PTH.

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 Calcitonin...
• This hormone will stimulate movement of calcium into the
bone structure.
• It can also be used therapeutically for the treatment of
hypercalcemia or osteoporosis.
• Without this hormone calcium will stay within the blood
instead of moving into bones to keep them strong &
growing.

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Clinical correlates…

60
 Disorders of T3/T4
A. Hyper secretion: excessive T3/T4 [thyrotoxicosis]
Causes
 Excessive TSH
 Grave’s disease:
• Autoimmune disorder:
–Exerts TSH-like effects on thyroid.
Clinical features
• Weight loss, voracious appetite
• Over sweating, heat intolerance
• Visual disturbance
• Persistent tachycardia
• Nervousness
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 Disorders of T3/T4…
B. Hyposecretion of T3/T4 = Hypothyroidism
Causes
• Primary thyroid disease
• Secondary to ↓↓TSH
• Autoimmune disease
Clinical features
 Myexedema (adult)
- Accumulation of mucoproteins and fluid in subcutaneous tissue.
 Cretinism (children)
– Hypothyroid from end of 1st trimester to 6 months postnatally.
• Severe mental retardation.
 Cold intolerance
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 Goiter
• Enlargement of thyroid gland
• Associated with hyper/hypothyroidism.
Causes
1. Endemic goiter: caused by I-deficiency
2. Drug induced goiter: caused by goiterogenic or
antithyroid sub
3. Thyroiditis induced goiter: caused by autoimmune
4. Physiologic goiter: puberty, pregnancy
5. Toxic goiter: caused by over activity of pituitary,
unresponsiveness of pitutary to T3/T4, hyperactivity of
the thyroid gland.
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Iodine-deficiency
(endemic) goiter:
• Abnormal growth of the
thyroid gland.
In the absence of sufficient
iodine, cannot produce
adequate amounts of T4 & T3.
Lack of negative feedback
inhibition stimulates TSH,
which causes abnormal
growth.

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 4. Parathyroid gland
• Small, light-coloured lumps that stick out from the surface
of the thyroid gland.
• Are 4 glands located on the thyroid gland.
• They are butterfly-shaped & located inside the neck, more
specifically on both sides of the windpipe.
• One of the most important functions of this gland is to
regulate the body's calcium & phosphorus levels.

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 Parathyroid gland...
• There are 2 major types of cells that make up parathyroid tissue:
1. Oxyphil cells: major cells but function is unknown.
2. Chief cells: produce parathyroid hormone (PTH).
• PTH finds its major target cells in:
– bone, kidneys & gastrointestinal system
• PTH causes release of ca++ present in bone to the ECF.
• ↓ Osteoblasts (production of bone) &
• ↑ Osteoclasts (removal of bone).
– Signals the kidneys to reabsorb more of this mineral,
transporting it into the blood.
– Signals the small intestine to absorb more of this mineral,
transporting it from the diet into blood.
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 Parathyroid gland...

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 Parathyroid gland...
• The adult body contains as much as 1kg of ca++, most of
this calcium is found in bone & teeth.
• ca++ is important for :
– body metabolism, blood clot, skeletal muscles
contraction...
• If parathyroid glands are removed accidentally during
surgery on the thyroid, there would be a drop in the ca++
concentration
– as more ca++ is excreted by the kidneys & intestines, &
more incorporated into the bone.

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 Parathyroid gland...
• This can produce serious disturbances, particularly in the
muscles & nerves, which use ca++ for normal functioning.
• Over activity of the parathyroid glands, which can result
from a tumour on the glands, produces a weakening of the
bones.
– This is a condition that makes them much more
vulnerable to fracturing because of excessive
withdrawal of calcium from the bones.

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 7-Dehydrocholestrol
Sun light
3- Cholecalciferol (Vit-D3)
Liver enzyme 25-α Hydroxylase
25-Hydroxycholecalciferol
Kidneys proximal 1 α-Hydroxylase
tubules Stimulated by PTH
1, 25-(OH)2 D3(vitamin D3)
↑ Synthesis of Ca-binding proteins
↑Ca absorption in GIT
↑Ca reabsorption in renal tubules
 Summary of Ca-homeostasis

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 5. Adrenal glands

• Triangular-shaped glands located on top of the kidneys.

• Through hormonal secretions, they regulate many essential
functions in the body, including:
– biochemical balances that influence:
• Athletic training &
• General stress response.

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 Adrenal glands...
• Produce hormones like:
– Aldosterone
– Cortisol
– Androgens
• Produces chemicals like:
– Adrenalin/epinephrine
– Noradrenalin/norepinephrine
– Dopamine

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 Adrenal Cortex
• The hormones made by the adrenal cortex supply long-
term responses to stress.
• The cortex of the adrenal gland is known to produce over
20 hormones, but their study can be simplified by
classifying them into three categories:

1. Glucocorticoids ...... Cortisol

2. Mineralocorticoids ... Aldosterone
3. Sex hormones ....... Androgen

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 Adrenal Cortex ...
1. Mineralocorticoids (Aldosterone)
– regulate the salt & water balance, leading to the increase
of blood volume & pressure.
2. Glucocorticoids (Cortisol)
– raise blood glucose level, stimulates breakdown of
protein.
3. Sex Hormones (Androgen)
– stimulates reproductive organs & brings on sex
characteristics.

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 Mineralocorticoids: Aldosterone
• Aldosterone is the prototype example of
mineralocorticoids
• 60% is transported bound with plasma proteins
– Shorter half life: 20minutes
• Plasma concentration: 6ng/dl
• Secretion is mainly controlled by potassium and Ang-II
level in plasma

76
 Functions of aldosterone
1. ↑Na+ reabsorption by renal tubule
• ↑Aldosterone = ↑Na+ = ↑Osmolality = ↑ADH
2. ↑Tubular hydrogen ion secretion in intercalated cells of
cortical collecting tubules
– If excess it leads to metabolic alkalosis
3. ↑K+ secretion by principal cells of collecting tubules and distal
tubules
– Stimulates K+ transport from ECF to cells
– If aldosterone is excess it may lead to hypokalaemia (<
2meq/L)
• Muscle weakness
– If aldosterone is deficient= Hyperkalemia
• Cardiac toxicity 77
 Functions of aldosterone…
4. Aldosterone increases NaCl reabsorption by sweat &
salivary ducts & secretion of HCO3- and K+
5. Aldosterone enhances Na absorption by intestines,
particularly in large intestine

78
 Glucocorticoids
• Cortisol, cortisone, corticosterone
• Influence metabolism & mediate response to stress
• Cortisol is secreted in major amounts
• Non-stress: CRH, ACTH, cortisol release, negative feedback
• Stress: Sympathetic NS overrides inhibitory effects of high
cortisol levels and triggers CRH release
• 95% activities of glucocorticoids
• 90-95% is transported bound to cortisol binding globulin or
Transcortin
– 60-90 minutes half life
• Plasma level: 12 μl/dl
• Metabolized in liver
79
 Physiologic effects of cortisol
• Produced in response to stress
1. Metabolic Effects
a. On carbohydrates
– Gluconeogenesis hence ↑BGC
– Decreases glucose utilization by cells
• By decreasing translocation of GLUT4
» Adrenal Diabetes
b. On protein metabolism
– ↑Catabolism & decreases anabolism
• Reduces protein stores in almost all extrahepatic tissues
• Increases amino acid mobilization from extrahepatic
tissues to ECF
– ↑Liver and plasma proteins 80
 Physiologic effects of cortisol…
c. On fat metabolism: ↑Lipolysis
– Increases fatty acid mobilization from adipocytes
• Increased FA in plasma
• Increased fat utilization for energy
2. Anti-inflammatory effect
– Immunosuppressant effect
– Inhibit lymphocyte activation & proliferation
– Stabilization of lysosomal membrane

81
 Physiologic effects of cortisol…
4. Enhances catecholamines synthesis & release
5. Anti-allergic action
6. Growth inhibitory effect
7. ↑HCl secretion, contributes to PUD
8. Stimulates surfactant production in lungs

82
 Effects of stress on a body
Stress

Nerve Hypothalamus
Spinal cord
signals
(cross section) Releasing
hormone
Nerve
cell
Anterior pituitary
Blood vessel

Nerve cell

ACTH

Adrenal
gland
Kidney

(A) SHORT-TERM STRESS RESPONSE (B) LONG-TERM STRESS RESPONSE

Effects of epinephrine & norepinephrine:
Effects of Effects of
1. Glycogen broken down to glucose; glucocorticoids:
mineralocorticoids:
increased BG 1. Proteins & fats broken
1. Retention of Na+ down & converted to
2. Increased BP, RR, MR
& H2O by kidneys glucose, leading to
5. Change in blood flow patterns, leading 2. Increased blood increased blood glucose
to increased alertness & decreased volume & BP 2. Immune system
digestive & kidney activity suppressed
 Adrenal Medulla

• The effects of these hormones provide a short-term

response to stress.
• Hypothalamus starts nerve impulses that
travel the path from the bloodstream, spinal cord &
sympathetic nerve fibers to the adrenal medulla, which
then releases hormones:
– Epinephrine
– Norepinephrine

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 Catecholamine's
• Epinephrine and Norepinephrine
• Produced by adrenal medulla
• Stimulated by sympathetic nervous system
– Sympathoadrenal system
• Both derived from hydroxylation of tyrosine
• Both water soluble
• Their receptors are at cell membrane

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 Physiologic effects of catecholamines
1. Increases heart activity
2. Bronchodilation
3. Inhibits GI motility
4. ↑Mental alertness
5. ↑blood glucose level
↑ Lipolysis, ↑Utilization of fat
↑ Protein catabolism
6. ↑Metabolic rate (MR)

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 6. Pancreas
• Very important organ in the digestive system & circulatory
system to maintain blood sugar levels.
• It is both an exocrine & an endocrine organ.
• As an exocrine organ; it is considered to be part of the
gastrointestinal system.
– It produces digestive enzymes to be released into the
small intestine
aid in reducing food particles to basic elements that
can be absorbed by the intestine & used by the body.

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 Pancreas ...
• Pancreas also has a very important endocrine function.
– Insulin & glucagon [regulate blood sugar levels].
• Groups of endocrine cells (Islets of Langerhans) secrete
two hormones.
1. Beta cells [β]: secrete Insulin
2. Alpha cells [∂]: secrete Glucagon.
 These hormones are secreted directly into the
bloodstream to affect organs all over the body.
• The level of sugar in the blood depends on the opposing
action of these two hormones.

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 Pancreas ...
• Insulin
– acts to lower blood sugar levels by allowing the sugar to
flow into cells.
• Glucagon
– acts to 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.
– push-pull system.

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 Insulin and Its metabolic Effects
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
– Inhibits the breakdown of the proteins in the cell
3. On Cortisol
– Anticortisol effect =blood glucose by:
• inhibiting gluconeogenesis &
• activating glucose uptake
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 Glucose homeostasis disorders
 Diabetes mellitus = abnormalities on insulin.
• Syndrome characterized by hyperglycemia.
• Symptoms :
– Polyuria
• excessive urine production, glucose osmotic effect.
– Polydipsia
• excessive thirst & ↑ fluid intake, for compensation.
– Blurred vision due to high blood glucose effects on the
eye's optics.
– Unexplained weight loss.
– Lethargy (state of unconsciousness).
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 Types of Diabetes mellitus
Type I DM Type II DM
• Juvenile diabetes • Maturity onset diabetes
• Insulin dependent DM • Insulin resistance DM
• As the pancreas does not • The pancreas does
produce sufficient insulin, produce enough insulin,
it is treated by insulin but the target cells do not
injections. respond to it.

Complications of DM
- Cardiopathy, nephropathy, neuropathy & retinopathy,
gangrene [wound is unhealed].
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 7. Gonads
• Are testes in male & ovaries in female.
– Both of these organs produce & secrete hormones that
are balanced by the hypothalamus & pituitary glands.
• The main hormones from the reproductive organs are:
• Testosterone
• Estrogen
• Progesterone

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 Testosterone
• It is more prominent in males.
• It belongs to the family of androgens, which are steroid
hormones producing masculine effects.
• Stimulates the development & functioning of the primary
sex organs.
– testes & their connecting tubes & the prostate gland.
• Stimulate the development & maintenance of secondary
male characteristics:
– hair growth on the face &
– the deep pitch of the voice.

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 Estrogen
• It is more prominent in females.
• Mainly produced by Ovaries.
• Increases at the time of puberty
• Stimulates the development of the uterus & vagina.
• Stimulates the development & functioning of the primary
sex organs.
– ovaries, fallopian tubes and the uterus.
• It is also responsible for the development & maintenance of
secondary female characteristics:
– fat distribution throughout the body &
– the width of the pelvis.
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 Progesterone
A female hormone secreted by the corpus luteum after
ovulation during the second half of the menstrual cycle.
Prepares the lining of the uterus for implantation of a
fertilized egg & allows for complete shedding of the
endometrium at the time of menstruation.
In the event of pregnancy, the progesterone level remains
stable beginning a week or so after conception.

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 8. Pineal gland
• Also called the pineal body or epiphysis.
• It is a small endocrine gland in the brain.
• The main hormone produced & secreted by the pineal gland is
melatonin.
• Production is stimulated by the suprachiasmatic nucleus (SCN)
in hypothalamus(primary center for circadian rhythms)
 Light/dark changes required to synchronize.
Secretion is highest at mid night & b/n the ages of 0-5 years.
Regulates the sleep-wake cycle by causing drowsiness and
lowering the body temperature
Regulates the release of reproductive hormones in females. For
example, the timing, length, and frequency of menstrual cycles
in women are influenced by melatonin
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 9. Thymus gland
• Hormone: Thymopoietin
• Function:
– Stimulates lymphocyte proliferation.
• Lymphocytes are involved in cell-mediated immunity.

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10. Other organs having endocrine function
1. Heart:
Hormone: ANP (atrial natriuretic peptide)
Function:
 increase natriuresis & GFR
 decrease rennin & aldosterone secretion
 vasodilator
2. Liver
Hormones:
 Erythropoietin, Somatomedin-C, Calcitriol

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Other organs having endocrine function…
3. Kidneys
 Hormones: Erythropoietin , Calcitriol
 Function: RAS Ang-I Ang-II
 Ang-II
A potent vasoconstrictor
Aldosterone & ADH secretion
Stimulates the thirst center
Salt and water reabsorption
4. GIT hormones: Gastrin, Secretin, CCK, VIP, etc.

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 THANK YOU!!!

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