Hormone

Endocrine System

There are two system in the body which contribute to homeostasis by controlling
and coordinating various organ and physiological function.

Endocrine System
Nervous system
Together known as NEURO ENDOCRINE SYSTEM
• Chemical produced by endocrine glands and released in to
the blood and transported to a distinctly located target
organ.
Current

Hormones are non nutrient chemical which act as intercellular messengers and produce in trace
amount.
• Endocrine System

• Endocrine—endo means within. This is a system which controls body function througn
hormones.
• Endocrine System is composed of a number of glands.

• Glands are specialized tissues that produce a hormone.

What are target cells?

• Target cells refer to cells that contain specific receptors (bind sites) for a particular hormone.
Once a hormone binds to receptors on a target cell, a series of cellular events unfold that
eventually impact gene expression and protein synthesis.
What are hormone receptors?

Hormone receptors are binding sites on the target cell (either on the surface or in the cytoplasm
or nucleus of the target cell) that are activated only when specific hormones bind to them. If a
hormone does not/cannot bind to it’s receptor, then no physiologic effect results.
Classification of hormones

Hormones can be classified according to the

Chemical nature,
Mechanism of action,
Nature of action,
Stimulation of Endocrine glands and
Effects of hormones
Chemical nature of hormones

• 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).
Nature of hormones action
• A. Local hormones-These hormones have a specific local effect through paracrine secretion, for example,
hormone testosterone
• These act locally on neighboring cells or on the same cell that secretes them without first entering the
bloodstream.
• b. General hormones-These are hormones transported through circulation to the distal target tissue/organ
examples are thyroid hormones and insulin.
• 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

Tropic hormones
1. Their primary function is to act at different endocrine glands than those from which are secreted, maintaining their integrity and regulating the secretion of
other hormones.

2. In the absence of these hormones their endocrine target tissues lose their structural integrity and stop secreting their h ormones.
3. Example: Thyroid-stimulating hormone (TSH)

Non-tropic hormones

1. They do not regulate the secretion of other hormones. They directly stimulate target cells to induce effects.

2. Example: Insulin, catecholamines.

Chemical Structure of Hormones
• Two general classes of hormones: water solub’ and lipid soluble.

• Water soluble (polar): proteins, glycoproteins, polypeptides, amino acid derivatives.

• Lipid soluble (nonpolar): steroids, amino acid derivatives, fatty acids.

• Different classes have different mechanisms of action, different modes of transport through
the body, and differing stability in the circulation.
• Examples of Lipid-Soluble Hormones

• Steroids: estrogen, progesterone, testosterone, glucocorticoids, mineralocorticoids

• Amino acid derivatives: Thyroid hormones (T3, T4)

• Fatty acids: prostaglandins, thromboxanes

• Examples of Water Soluble Hormones

• Proteins: growth hormone, prolactin, insulin

• Glycoproteins: follicle-stimulating hormone (FSH), luteinizing hormone (LH), thyroid-

stimulating hormone (TSH)
• Polypeptides: arginine vasopressin, oxytocin, somatostatin

• Amino acid derivatives: epinephrine, melatonin

Cell Signaling

Autocrine
The hormone act on the cell that secreted it.
Paracrine: The hormone act on a nearby cell without having to enter the blood circulation.
Intracrine: The hormone is produced in the cell and acts intracellularly means inside the cell.
Endocrine: The hormone act on the target cells once it is released from the respective glands
into the bloodstream
Endocrine Glands

• The endocrine glands include the

• Pituitary

• Thyroid

• Parathyroid

• Adrenal

• Pineal glands.
• Several organs and tissues are not exclusively classified as endocrine glands but contain cells that secrete
hormones.
• These include

• Hypothalamus

• Thymus

• Ovaries, testes

• Kidneys, stomach and pancreas

• Liver and small intestine,

• Skin, heart, adipose tissue, and placenta

Pituitary Gland “The Master gland of the body”

• Pituitary gland is the small structure in the head main endocrine gland.

• The normal adult pituitary gland is a reddish-grey bean shaped gland.

• It is also called the Master gland because it produces the hormones that control other glands
and many body functions including growth.
• Anatomy of Pituitary Gland:

• The pituitary gland is a pea sized, weighs 500 mg l at the base of brain.

• It is 1em in diameter

• The pituitary gland lies in the Hypophyseal fossa (Sella turcica) of the Sphenoid bone below the
hypothalamus.
• A fold of durameter covers the pituitary gland and has an opening for the passage of
infundibulum (stalk) connecting the gland to the hypothalamus.
• Division of pituitary gland

• It consists of two main parts that originate from different type of cells.

• Anterior pituitary gland (Adeno hypophysis):

• It is an up growth of glandular epithelium from the pharynx.

• It secrete peptide hormones.

• Posterior pituitary gland (neurohypophysis):

• It is formed from the nervous tissue and nerve cells, surrounding by supporting glial cells (pituicytes).

• It stores hormones secreted by the hypothalamus.

Hormones produced by anterior pituita gland

• Growth hormone (GH)

• Thyroid-stimulating hormone (TSH)

• Adrenocorticotrophic hormone (ACTH)

• Prolactin (PRL)

• Gonadotrophins

• I. Luteinizing hormone (LH)

• II. Follicle-stimulating hormone (FSH)

• Growth hormone:

• Its release is stimulated by GHRH (growth hormone releasing hormone) suppressed by GHRIH
(g hormone release inhibiting hormone) secreted hypothalamus.
• Secretion is also stimulated by hypoglycemia, exercise and anxiety.

• Secretion is greater during night sleep than day.

• GHRIH also suppress the secretion of TSH and gastrointestinal secretion, e.g. Gastric juice,
gastrin and cholecystokinin.
Thyroid Stimulating Hormone(TSH

• The release of this hormone is stimulated by the Thyrotrophin Releasing Hormone(TRH) from
hypothalamus.
• It stimulates the growth and activity of thyroid gland.

• Thyroid gland secretes the thyroxine (T4) and Tri-Iodothyronine (T3).

• Its level is highest during the night.

• When blood level of thyroid hormone is high, secretion of TSH is reduced.

• Adrenocorticotrophic hormone(AC1
• ACTH secretion is stimulated by the release of Corticotrophin releasing hormone(CRH) hypothalamus
• ACTH level is highest at midday and lowest at midnıgını.
• It stimulates the synthesis and secretion of adrenal cortical hormone.
• It is stimulated by the hypoglycemia, stress, exercise and other emotional states..
• Its secretion is suppressed when blood level of ACTH rises.
• Prolactin
• This hormone is secreted during pregnancy for lactation.
• It is stimulated by prolactin releasing hormone from hypothalamus.
• After birth suckling stimulate the Prolactin secretion and lactation.
• Gonadotrophins (FSH and LH)

• Just before puberty two Gonadotrophins are secreted in gradually increasing amounts by the
anterior pit gland.
• Its secretion is stimulated by Gonadotrophin releasing hormone (GnRH) or luteinizing
hormone(LRH) from hypothalamus. Releasing
• Rising level of this hormone during puberty enhances the maturation of reproductive organs
• Luteinizing hormone(LH)

• IN FEMALES:

• LH and FSH stimulate the secretion of Oestroge-Progesterone from corpus luteum during the me
cycle.
• As the level of oestrogen and progesterone rises in blood, secretion of LH and FSH is suppressed.

• IN MALES:

• LH also called interstitial cell stimulated releasing hormone (ICSH).

• It stimulates the interstitial cells to secrete testosterone.

Posterior Pituitary Gland
Posterior pituitary hormones are synthesized in the nerv υυπό bodies, transported along the axons
and stored in vesicles within the axon terminals in the posterior pituitary glan

Nerve impulses from hypothalamus trigger the exocy. Vesicles (of pituitary gland) releasing their
hormone into blood stream.

Axon terminal release these two hormone within the posterior pituitary gland.
1. Oxytoxin
2. Antidiuritic hormone (ADH, Vasopressin)
• Oxytocin

• It is also called anti stress hormone.

• Oxytocin is produced in both males and females, main physiological roles seem to take place in the f In the female,
oxytocin is involved in a number of important physiological actions:
• 1. Stimulates the contraction of the uterus (myometrium)

• 2. Stimulates the contraction of the myoepithelial cells that eject milk from the breast.

• Uterine muscle contraction

• Sensory stretch receptors in the uterine cervix (due to baby’s head) stimulate the release of oxytocin.

• Oxytocin stimulates the more forceful contract cervix, as the baby’s head is forced further downwards.

• It is also used clinically for the induction of labor.

• Milk Ejection

• Suckling generates sensory impulses that are transmitted from breast to the hypothalamus.

• This impulses triggers the release of oxytocin posterior pituitary gland.

• Oxytocin stimulates the contraction of the milk ducts and myoepithelial cells for ejection of milk.

• Suckling also inhibits the release of Prolactin inhibiting hormone (PIH) prolonging Prolactin secretion and lactation.
Antidiuritic Vasopressin).
Hormone
The main effect of the antidiuretic hormone is to reduce urine output (diuresis is the production
of a large a of urine) therefore it is called Antidiuritic.
Its secretion is determined by osmotic pressure by circulating osmoreceptors in blood.
Incrase water intake > decrease in ADH > increase in urine output.
Decrease in water intake > Increase in ADH > Decrease in urine output. The main effect of the
antidiuretic hormone is to reduce urine output (diuresis is the production of a large a of urine)
therefore it is called Antidiuritic.Its secretion is determined by osmotic pressure by circulating
osmoreceptors in blood.Increase water intake > decrease in ADH > increase in urine
output.Decrease in water intake > Increase in ADH > Decrease in urine output
INTRODUCTION

• The adrenal glands develop from two separate embryological tissues; the neural crest
ectoderm and the intermediate mesoderm.
• The medulla originates from neural crest cells. The adrenal cortex develops from the
intermediate mesoderm.
• The fetal cortex develops in the centre, with the permanent cortex surrounding it.

• By 4 months of age the adrenal gland is fully developed

Position and location
The adrenal glands located on the upper poles of each kidney on the right and left sides
They are covered by peritoneum on the posterior abdominal wall they are embedded into pre renal fat
The left one is larger and higher than the right
Adrenal gland measures :-
Location of the Adrenal Glands
Width 3 cm Length 5 cm
Thickness 1 cm Weight 7-10 gm
adrenal glands kidneys
Colour-yellowish
ANATOMY OF ADRENAL GLANDS

• The adrenal glands are paired bodies lying cranial to the kidneys within the retroperitoneal
space. The glands consist of two layers;
• 1. cortex

• II. medulla
ADRENAL CORTEX

• The adrenal cortex is red to light brown in colour and is composed of zones. From the outer to
innei layers are;
• 1. zonaglomerulosa- is narrow and the cells are in a whorled pattern.

• 2. zonafasciculata- wide and the cells lie in columns and

• 3. zonareticularis-organised. More randomly

• The adrenal cortex represents 80-90% of the adrenal gland.

• The adrenal medulla represents only 10-20% of the adrenal gland.

• HORMONES OF THE ADRENAL CORTEX

• The adrenocortical hormones and their functi the body are classified into:

• 1. Mineralocorticoids

• 2. Glucocorticoids

• 3. Adrenal androgens
MINERALOCORTICOID
• These hormones help to control the water and electrolyte homeostasis, particularly the concentration of Na+ and K+ io
Mineralocorticoids include the following hormones:
• They are produced in the zona glomerulosa.
• The primary mineralocorticoid is aldosterone. Its secretion is regulated by the oligopeptide angiotensin II (angiotensin II is regulated by
angiotensin I, which in turn is regulated by renin).
• Aldosterone is secreted in response to high extracellular potassium levels, low extracellular sodium levels, and low fluid levels and
blood volume.
• Aldosterone affects metabolism in different ways:
• It increases urinary excretion of potassium ions.
• It increases interstitial levels of sodium ions.
• It increases water retention and blood volume.
GLUCOCORTICOIDS
• They are produced in the zona fasciculata.

• The primary glucocorticoid released by the adrenal gland in the human is cortisol and corticosterone in many other animals.

• Its secretion is regulated by the hormone ACTH from the anterior pituitary.

• Upon binding to its target, cortisol enhances metabolism in several ways:

• It stimulates the release of amino acids from the body

• It stimulates lipolysis, the breakdown of fat

• It stimulates gluconeogenesis, the production of glucose from newly-released amino acids and lipids
• It increases blood glucose levels in response to stress, by inhibiting glucose uptake into muscle and fat cells

• It strengthens cardiac muscle contractions

• It increases water retention

• It has anti-inflammatory and anti-allergic effects

• 3. ANDROGEN

• Androgen, also called androgenic hormones or testoids, is the generic term for any natural or syntheti
compound, usually a steroid hormone, that stimulates c. Controls the development and maintenance of male
characteristics in vertebrates by binding to androgen receptors.
• This includes the activity of the accessory male sex organs and development of male secondary sex
characteristics.
• Androgens were first discovered in 1936.

• Androgens are also the original anaboli steroids and the precursor of all estrogens, the female sex hormones.
Adrenal medulla

• The adrenal medulla is part of the adrenal gland.

• It is located at the center of the c being surrounded by the adrenal cortex.

• It is the inner most part of the adrenal gland, consisting of cells that secrete epinephrine,
norepinephrine, and a small amount of dopamine in response to stimulation by sympathetic
preganglionic neurons
• Function

• Rather than releasing a neurotransmitter, the cells of the adrenal medulla secrete hormones.

• Composed mainly of hormone-producing chromaffin cells, the adrenal medulla is the principal
site of the conversion of the amino acid tyrosine into the catecholamines adrenaline
(epinephrine), noradrenaline (norepinephrine), and dopamine.
Epinephrine (Also called adrenaline)

Epinephrine (also known as adrenaline) is a hormone and neurotransmitter.

It increases heart rate, contracts blood vessels, dilates air passages and participates in the fight-or-
flight response of the sympathetic nervous system.Chemically, epinephrine is a catecholamine, a
monoamine produced only by the adrenal glands from the amino acids phenylalanine and tyrosine.

The term adrenaline is derived from the Latin roots ad- and renes and literally means on the kidney,
in reference to the adrenal gland’s anatomic location on the kidney.
Norepinephrine (Also called noradrenaline.)
• Norepinephrine (INN) (abbreviated norepi or NE) or noradrenaline (BAN) (abbreviated NA or Nad) is a catecholamine
with multiple roles including as a hormone and a neurotransmitter.
•

• As a stress hormone, norepinephrine affects parts of the brain where attention and responding actions are controlled.

• Along with epinephrine, norepinephrine also underlies the fight-or-flight response, directly increasing heart rate,
triggering the release of glucose from energy stores, and increasing blood flow to skeletal muscle.
•

• Norepinephrine can also suppress neuroinflammation when released diffusely in the brain from the locus ceruleus.
• This is not a major endocrine structure however produces hormones along with performing its main function
• (a) thymus
• (b) kidneys
• (c) pancreas
• (d) pituitary
• FSH is produced by __________
• a) Thyroid gland
• b) Anterior pituitary gland
• c) Posterior pituitary gland
• d) Gonads
• Which of the following hormone is produced by a pituitary gland in both males and females but functional only in a female?
• A) Relaxin
• b) Prolactin
• c) Vasopressin
• d) Somatotrophic hormones
• Which of the following is an accumulation and releasing centre of neurohormone?
• A) Hypothalamus
• b) Anterior lobe of pituitary gland
• c) Posterior pituitary gland
• d) Intermediate lobe of pituitary
MSH is produced by _________
a) Anterior lobe of pituitary gland
b) Posterior pituitary gland
c) Parathyroid
d) Pars intermedia of pituitary
Trophic hormones are formed by _________
a) Anterior pituitary
b) Middle pituitary
c) Thyroid
d) Posterior pituitary
• Which hormone causes the contraction of labor?
• A) Prolactin
• b) Estrogen
• c) Progesterone
• d) Oxytocin
• What is Sheeshan’s syndrome?
• A) The pituitary adenoma is hemorrhagic and necrotic
• b) Pituitary gland is infected with virus
• c) Pituitary gland is infected with Bacteria
• d) It is the malignancy of the pituitary
Which of the following is not released by anterior pituitary gland?
A) Prolactin
b) ADH
c) FSH
d) TSH
Which of the following hormone is known as flight and fight hormone?
A) Thyroxin
b) Adrenaline
c) ADH
d) Oxytocin
• Adrenal gland is derived from ________
• a) Endoderm
• b) Mesoderm
• c) Ectoderm
• d) Ectoderm and mesoderm
• Adrenaline hormone increases ________
• a) Blood pressure
• b) Blood glucose level
• c) Arteriosclerosis
• d) Oxygen uptake
• What is the name of the cells producing the hormone in adrenal medulla?
• A) F cells
• b) Chief cells
• c) Principal cells
• d) Chromaffin cells
• Which is not the function of cortisol?
• A) Increases glucose uptake by muscles
• b) Convert amino acids to glucose
• c) Converts fat to fatty acids
• d) Increases blood sugar level in response to stres
• ACTH controls the secretion of ________
• a) Cortisol
• b) Aldosterone
• c) Epinephrine
• d) Testosterone
• Which is the outer most layer of the Adrenal cortex part and what it secretes?
• A) Zona Glomerulosa and secretes Mineralocorticoids
• b) Zona Glomerulosa and secretes Glucocorticoids
• c) Zona Reticularis and secretes Mineralocorticoids
• d) Zona Reticularis and secretes Mineralocorticoids