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E ENDOCRINE SYSTEM

All the physiological activities of the body are regulatedby two major systems

1. Nervous system

2. Endocrine system.

These two systems interact with one another and regulate the body functions. Endocrine system
functions by secreting some chemical substances called hormones.

ENDOCRINE GLANDS

Endocrine glands are the glands which synthesize and release the classical hormones into the
blood. Endocrine glands are also called ductless glands because the hormones secreted by
them are released directly into blood without any duct. Endocrine glands are distinct from
exocrine glands which release their secretions through ducts.
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HORMONES RELEASED FROM ENDOCRINE GLANDS

Growth hormone (GH)

Thyroid stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
PITUITARY GLAND
Follicle stimulating hormone (FSH)
Luteinizing hormone (LH)
Anterior pituitary gland
Prolactin
Melanocyte stimulating hormone (MSH)

Antidiuretic hormone (ADH) or vasopressin & Oxytocin

posterior pituitary gland

THYROID GLAND Thyroxine (T4) & Triiodothyronine (T3)

PARATHYROID GLAND Parathormone & Calcitonin

PANCREAS – ISLETS OF Insulin, Glucagon

LANGERHANS Somatostatin & Pancreatic polypeptide

Mineralocorticoids
ADRENAL GLAND Aldosterone & 11deoxycorticosterone
Glucocorticoids
Adrenal cortex Cortisol &Corticosterone

Catecholamines
Adrenal medulla Adrenaline(Epinephrine),Noradrenaline
(Norepinephrine)& Dopamine

GONADS Testosterone & Dihydrotestosterone

Testis
Estrogen & Progesterone
Ovary
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HORMONES
Hormones are chemical messengers, synthesized by endocrine glands. Based on chemical
nature, hormones are classified into three types
1. Steroid hormones

2. Protein hormones
3. Derivatives of the amino acid called tyrosine

STEROID HORMONES

Steroid hormones are the hormones synthesized from cholesterol or its derivatives. Steroid
hormones are secreted by adrenal cortex, gonads and placenta.

• Aldosterone
• Cortisol

• Corticosterone

• Testosterone
• Dihydrotestosterone

• Estrogen

• Progesterone
PROTEIN HORMONES
Protein hormones are large or small peptides. Protein hormones are secreted by pituitary gland,
parathyroid glands, pancreas and placenta

• Growth hormone (GH) Parathormone

• Follicle-stimulating hormone
• Calcitonin
(FSH)
• Insulin
• Luteinizing hormone (LH)
• Glucagon • Prolactin
• Somatostatin • Antidiuretic hormone (ADH)
• Pancreatic polypeptide • Oxytocin

• Human chorionic gonadotropin (HCG)

• Thyroid-stimulating hormone (TSH)

• Adrenocorticotropic hormone (ACTH)
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TYROSINE DERIVATIVES
Two types of hormones, namely thyroid hormones and adrenal medullary hormones are derived
from the amino acid tyrosine

• Thyroxine (T4)

• Triiodothyronine (T3)

• Adrenaline (Epinephrine)
• Noradrenaline (Norepinephrine)

• Dopamine

PITUITARY GLAND

Pituitary gland or hypophysis is a

small endocrine gland with a
diameter of 1 cm and weight of 0.5
to 1 g.

It is situated in a depression called

‘sella turcica’, present in the
sphenoid bone at the base of skull.
It is connected with the
hypothalamus by the pituitary stalk
or hypophyseal stalk.

DIVISIONS OF PITUITARY GLAND

Pituitary gland is divided into two divisions
1. Anterior pituitary or adenohypophysis

2. Posterior pituitary or neurohypophysis.

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ANTERIOR PITUITARY GLAND

The anterior pituitary or adenohypophysis secretes hormones that regulate a wide range of
bodily activities, from growth to reproduction.
Release of anterior pituitary hormones is stimulated by releasing hormones and suppressed by
inhibiting hormones from the hypothalamus.

Types of Anterior Pituitary Cells and Their Hormones

Five types of anterior pituitary cells—somatotrophs, thyrotrophs, gonadotrophs, lactotrophs,
and corticotrophs—secrete seven hormones
1. Somatotrophs - secrete human growth hormone (hGH), also known as somatotropin.
Human growth hormone in turn stimulates several tissues to secrete insulin like growth factors,
hormones that stimulate general body growth and regulate metabolism.

2. Thyrotrophs - secrete thyroid-stimulating hormone (TSH), also known as thyrotropin . TSH

controls the secretions and other activities of the thyroid gland.
3. Gonadotrophs – secrete two gonadotropins: follicle-stimulating hormone (FSH) and
luteinizing hormone (LH) , FSH and LH both act on the gonads.

They stimulate secretion of estrogens and progesterone and the maturation of oocytes in the
ovaries, and they stimulate sperm production and secretion of testosterone in the testes.

4. Lactotrophs - secrete prolactin (PRL), which initiates milk production in the mammary
glands.

5. Corticotrophs - secrete adrenocorticotropic hormone (ACTH), also known as corticotropin

, which stimulates the adrenal cortex to secrete glucocorticoids such as cortisol.
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FUNCTIONS OF ANTERIOR PITUTARY HORMONES

1. Thyroid-Stimulating Hormone

• Thyroid-stimulating hormone (TSH) stimulates the synthesis and secretion of the two
thyroid hormones triiodothyronine (T3) and thyroxine (T4), both produced by the
thyroid gland.

• Thyrotropin releasing hormone (TRH) from the hypothalamus controls TSH secretion.
• Release of TRH in turn depends on blood levels of T3 and T4 high levels of T3 and T4
inhibit secretion of TRH via negative feedback.
2. Follicle-Stimulating Hormone

• In females, the ovaries are the targets for follicle-stimulating hormone (FSH). Each
month FSH initiates the development of several ovarian follicles

• FSH also stimulates follicular cells to secrete estrogens (female sex hormones).
• In males, FSH stimulates sperm production in the testes.
• Gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates FSH
release.

• Release of GnRH and FSH is suppressed by estrogens in females and by testosterone

(the principal male sex hormone) in males through negative feedback systems. There is
no gonadotropin-inhibiting hormone
3. Luteinizing Hormone

• In females, luteinizing hormone (LH) triggers ovulation, the release of a secondary

oocyte (future ovum) by an ovary.

• LH stimulates formation of the corpus luteum (structure formed after ovulation) in the
ovary and the secretion of progesterone (another female sex hormone) by the corpus
luteum.

• Together, FSH and LH also stimulate secretion of estrogens by ovarian cells.

• Estrogens and progesterone prepare the uterus for implantation of a fertilized ovum and
help prepare the mammary glands for milk secretion.

• In males, LH stimulates cells in the testes to secrete testosterone. Secretion of LH, is

controlled by gonadotropin-releasing hormone (GnRH).

4. Prolactin

• Prolactin (PRL), together with other hormones, initiates and maintains milk production
by the mammary glands.

• Ejection of milk from the mammary glands depends on the hormone oxytocin, which
is released from the posterior pituitary.

• Together, milk production and ejection constitute lactation.

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• The function of prolactin is not known in males, but its hypersecretion causes erectile
dysfunction (impotence, the inability to have an erection of the penis).

• In females, hypersecretion of prolactin causes galactorrhea (inappropriate lactation) and

amenorrhea (absence of menstrual cycles).
5. Adrenocorticotropic Hormone

• Corticotrophs secrete mainly adrenocorticotropic hormone (ACTH). ACTH controls

the production and secretion of cortisol and other glucocorticoids by the cortex (outer
portion) of the adrenal glands.
• Corticotropin-releasing hormone (CRH) from the hypothalamus stimulates secretion of
ACTH by corticotrophs.
• Stress-related stimuli, such as low blood glucose or physical trauma, stimulate release
of ACTH.

6. Human Growth Hormone

• Somatotrophs are the most numerous cells in the anterior pituitary, and human growth
hormone (hGH) is the most plentiful anterior pituitary hormone.
• GH is responsible for the growth of almost all tissues of the body, which are capable of
growing.
• It increases the size and number of cells by mitotic division. GH also causes specific
differentiation of certain types of cells like bone cells and muscle cells.

7. Melanocyte-Stimulating Hormone
• Melanocyte-stimulating hormone (MSH) increases skin pigmentation in amphibians by
stimulating the dispersion of melanin granules in melanocytes. Excessive levels of
corticotropin-releasing hormone (CRH) can stimulate MSH release
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POSTERIOR PITUITARY GLAND

the posterior pituitary or neurohypophysis

does not synthesize hormones, it does store and
release two hormones It consists of axons and
axon terminals of more than 10,000
hypothalamic neurosecretory cells.

The cell bodies of the neurosecretory cells are in

the paraventricular and supraoptic nuclei of the
hypothalamus;

their axons form the hypothalamohypophyseal

tract. This tract begins in the hypothalamus and
ends near blood capillaries in the posterior
pituitary

Oxytocin
• During and after delivery of a baby, oxytocin affects two target tissues: the mother’s
uterus and breasts.
• During delivery, stretching of the cervix of the uterus stimulates the release of oxytocin
which, in turn, enhances contraction of smooth muscle cells in the wall of the uterus
• after delivery, it stimulates milk ejection (“letdown”) from the mammary glands in
response to the mechanical stimulus provided by a suckling infant. The function of
oxytocin in males and in nonpregnant females is not clear
• It also be responsible, in part, for the feelings of sexual pleasure during and after
intercourse
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Antidiuretic Hormone

antidiuretic ( anti- against; uresis urination)

• Substance that decreases urine production. ADH causes the kidneys to return more
water to the blood, thus decreasing urine volume.
• In the absence of ADH, urine output increases more than tenfold, from the normal 1 to
2 liters to about 20 liters a day.
• Drinking alcohol often causes frequent urination because alcohol inhibits secretion of
ADH.
• ADH also decreases the water lost through sweating and causes constriction of
arterioles, which increases blood pressure.
• This hormone’s other name, vasopressin ( vaso- blood; -pressus to press), reflects this
effect on blood pressure.

DISORDERS OF ANTERIOR PITUITARY GLAND

HYPERACTIVITY OF ANTERIOR PITUITARY

1. Gigantism- Gigantism is the pituitary disorder characterized by excess growth of the

body. Gigantism is due to hypersecretion of GH in childhood or in pre-adult life before
the fusion of epiphysis of bone with shaft.
2. Acromegaly- Acromegaly is the disorder characterized by the enlargement, thickening
and broadening of bones, particularly in the extremities of the body.

Acromegalic or gorilla face: Face with rough features such as protrusion of supra
orbital ridges, broadening of nose, thickening of lips, thickening and wrinkles formation on
forehead and Enlargement of hands and feet

HYPOACTIVITY OF ANTERIOR PITUITARY

Dwarfism- Dwarfism is a pituitary disorder in children, characterized by the stunted growth.
Caused by Reduction in GH secretion in infancy or early childhood causes dwarfism.
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HYPOACTIVITY OF POSTERIOR PITUITARY

Diabetes Insipidus- Diabetes insipidus is a posterior pituitary disorder characterized by excess

excretion of water through urine.

Causes

• Lesion (injury) or degeneration of supraoptic and paraventricular nuclei of

hypothalamus

• Lesion in hypothalamo-hypophyseal tract

Signs and symptoms
▪ Polyuria
▪ Polydipsia
▪ Dehydration
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THYROID GLAND
• The butterfly-shaped thyroid gland is located just inferior to the larynx (voice box). It
is composed of right and left lateral lobes, one on either side of the trachea, that are
connected by an isthmus. The normal mass of the thyroid is about 30 g

• Microscopic spherical sacs called thyroid follicles make up most of the thyroid gland.
The wall of each follicle consists primarily of cells called follicular cells

The follicular cells produce two hormones:

thyroxine is also called tetraiodothyronine

or T4 because it contains four atoms of iodine

triiodothyronine or T3, which contains three

atoms of iodine.

T3 and T4 together are also known as thyroid

hormones.

A few cells called parafollicular cells or C

cells lie between follicles. They produce the
hormone calcitonin which helps regulate
calcium homeostasis.

FUNCTIONS OF THYROID HORMONES

1. ACTION ON BASAL METABOLIC RATE (BMR)
• Thyroxine increases the metabolic activities in most of the body tissues, except brain,
retina, spleen, testes and lungs.
• It increases BMR by increasing the oxygen consumption of the tissues. The action that
increases the BMR is called calorigenic action.
• In hyperthyroidism, BMR increases by about 60% to 100% above the normal level and
in hypothyroidism it falls by 20% to 40% below the normal level.
2. ACTION ON PROTEIN METABOLISM
• Thyroid hormone increases the synthesis of proteins in the cells.
3. ACTION ON CARBOHYDRATE METABOLISM
Thyroxine stimulates almost all processes involved in the metabolism of carbohydrate.
• Increases the absorption of glucose from GI tract
• Enhances the glucose uptake by the cells, by accelerating the transport of glucose
through the cell membrane
• Increases the breakdown of glycogen into glucose
• Accelerates gluconeogenesis.
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4. ACTION ON FAT METABOLISM

• Thyroxine decreases the fat storage by mobilizing it from adipose tissues and fat depots.
The mobilized fat is converted into free fatty acid and transported by blood.

5. ACTION ON GROWTH

• Thyroid hormones have general and specific effects on growth. Increase in thyroxine
secretion accelerates the growth of the body, especially in growing children.

• Lack of thyroxine arrests the growth. So, the height of the individual may be slightly
less in hypothyroidism.

• Thyroxine is more important to promote growth and development of brain during fetal
life and first few years of postnatal life.

• Deficiency of thyroid hormones during this period leads to mental retardation.

6. ACTION ON GASTROINTESTINAL TRACT

• thyroxine increases the appetite and food intake. It also increases the secretions and
movements of GI tract. So, hypersecretion of thyroxine causes diarrhea and the lack of
thyroxine causes constipation.

7. ACTION ON RESPIRATION

• Thyroxine increases the rate and force of respiration indirectly. The increased metabolic
rate (caused by thyroxine) increases the demand for oxygen and formation of excess
carbon dioxide. These two factors stimulate the respiratory centers to increase the rate
and force of respiration

8. ACTION ON HEART

• The thyroid hormones enhance some actions of the catecholamines (norepinephrine and
epinephrine) because they up-regulate beta receptors. For this reason, symptoms of
hyperthyroidism include increased heart rate, more forceful heartbeats, and increased
blood pressure.
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DISORDERS OF THYROID GLAND

HYPERTHYROIDISM
• Increased secretion of thyroid hormones is called hyperthyroidism.

Graves’ disease

• Graves’ disease is an autoimmune disease and it is the most common cause of

hyperthyroidism.

• In Graves’ disease, the B lymphocytes (plasma cells) produce autoimmune antibodies

called thyroid-stimulating autoantibodies (TSAbs). These antibodies act like TSH by
binding with membrane receptors of TSH and activating thyroid follicular cells. This
results in hypersecretion of thyroid hormones.

SYMPTOMS OF HYPERTHYROIDISM
Intolerance to heat as the body produces lot of heat due to increased basal metabolic rate
caused by excess of thyroxine
1. Increased sweating due to vasodilatation
2. Decreased body weight due to fat mobilization
3. Diarrhea due to increased motility of GI tract
4. Nervousness, extreme fatigue, inability to sleep, mild tremor in the hands
5. Exophthalmos
6. Tachycardia and atrial fibrillation

HYPOTHYROIDISM

Decreased secretion of thyroid hormones is called hypothyroidism. Hypothyroidism leads to

myxedema in adults and cretinism in children

Myxedema

• Myxedema is the hypothyroidism in adults, characterized by generalized edematous

appearance. Causes for myxedema Myxedema occurs due to diseases of thyroid gland,

• genetic disorder or iodine deficiency. In addition, it is also caused by deficiency of

thyroid-stimulating hormone or thyrotropin-releasing hormone
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Cretinism

Cretinism is the hypothyroidism in children, characterized by stunted growth.

Causes for cretinism

Cretinism occurs due to congenital absence of thyroid gland, genetic disorder or lack of iodine
in the diet.

GOITER

Goiter means enlargement of the thyroid gland. It occurs both in hypothyroidism and
hyperthyroidism.

Goiter in Hyperthyroidism – Toxic Goiter

Toxic goiter is the enlargement of thyroid gland with increased secretion of thyroid hormones,
caused by thyroid tumor.

Goiter in Hypothyroidism – Non-toxic Goiter

Non-toxic goiter is the enlargement of thyroid gland without increase in hormone secretion. It
is also called hypothyroid goiter

Based on the cause, the non-toxic hypothyroid , goiter is classified into two types.

1. Endemic colloid goiter- Endemic colloid goiter is the non-toxic goiter caused by iodine
deficiency. It is also called iodine deficiency goiter.

2. Idiopathic non-toxic goiter- Idiopathic non-toxic goiter is the goiter due to unknown cause.
Enlargement of thyroid gland occurs even without iodine deficiency. The exact cause is not
known.
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PARATHYROID GLANDS

Human beings have four parathyroid glands, which

are situated on the posterior surface of upper and
lower poles of thyroid gland.

Parathyroid glands are very small in size,

measuring about 6 mm long, 3 mm wide and 2 mm
thick, with dark brown color.

Microscopically, the parathyroid glands contain

two kinds of epithelial cells. The more numerous
cells, called chief (principal) cells, produce
parathyroid hormone (PTH), also called
parathormone. The function of the other kind of
cell, called an oxyphil cell, is not known in a
normal parathyroid gland.

Parathyroid Hormone
• Parathyroid hormone is the major regulator of the levels of calcium (Ca2), magnesium
(Mg2), and phosphate (HPO4 2) Ions in the blood. The specific action of PTH is to
increase the number and activity of osteoclasts.
• The result is elevated bone resorption, which releases ionic calcium (Ca2) and
phosphates (HPO42) into the blood.
• PTH also acts on the kidneys. First, it slows the rate at which Ca2 and Mg2 are lost
from blood into the urine.
• Second, it increases loss of HPO4 2 from blood into the urine. Because more HPO42 is
lost in the urine than is gained from the bones, PTH decreases blood HPO42 level and
increases blood Ca2 and Mg2 levels.
• A third effect of PTH on the kidneys is to promote formation of the hormone calcitriol
, the active form of vitamin D. Calcitriol, also known as 1,25- dihydroxyvitamin D3,
increases the rate of Ca2, HPO42, and Mg2 absorption from the gastrointestinal tract
into the blood.
• The blood calcium level directly controls the secretion of both calcitonin and
parathyroid hormone via negative feedback loops that do not involve the pituitary gland
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ADRENAL GLANDS

The paired adrenal (suprarenal) glands, one of which

lies superior to each kidney in the retroperitoneal
space have a flattened pyramidal shape. In an adult,
each adrenal gland is 3–5 cm in height, 2–3 cm in
width, and a little less than 1 cm thick, with a mass of
3.5–5 g

PARTS OF ADRENAL GLAND

Adrenal gland is made of two distinct parts:

1. Adrenal cortex: Outer portion, constituting 80% of

the gland

2. Adrenal medulla: Central portion, constituting 20%

of the gland.

HORMONES OF ADRENAL GLAND

ADRENAL CORTEX ADRENAL MEDULLA

1. Mineralocorticoids (aldosterone) catecholamines
2. Glucocorticoids (cortisol, 1. Norepinephrine
hydrocortison, corticosterone and 2. Epinephrine
cortisone) 3. small amount of dopamine.
3. Sex hormones

These two parts are different from each other in development, structure and functions.

Adrenal medulla develops from the neural crest, which gives origin to sympathetic nervous
system. So, its secretions and functions resemble that of sympathetic nervous system.

Adrenal cortex develops from the mesonephros, which give rise to the renal tissues. It
secretes entirely a different group of hormones known as corticosteroids.
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ADRENAL CORTEX
The adrenal cortex is subdivided into three zones, each of which secretes different hormones

The outer zone- zona glomerulosa(secrete

hormones called mineralocorticoids)

The middle zone- zona fasciculata (secrete

mainly glucocorticoids)

The inner zone- the zona reticularis

(synthesize small amounts of weak
androgens steroid hormones that have
masculinizing )effects.

Mineralocorticoids
Aldosterone is the major mineralocorticoid. It regulates homeostasis of two mineral ions
namely, sodium ions (Na) and potassium ions (K) and helps adjust blood pressure and blood
volume.
Aldosterone also promotes excretion of H+ in the urine, this removal of acids from the body
can help prevent acidosis (blood pH below 7.35)
Aldosterone has three important functions.
It increases:
1. Reabsorption of sodium from renal tubules
2. Excretion of potassium through renal tubules
3. Secretion of hydrogen into renal tubules.

The renin–angiotensin–aldosterone or RAAs pathway controls secretion of aldosterone

✓ Stimuli that initiate the renin–angiotensin–aldosterone pathway include dehydration,
Na_ deficiency, or hemorrhage.
✓ These conditions cause a decrease in blood volume.
✓ 3 Decreased blood volume leads to decreased blood pressure.
✓ Lowered blood pressure stimulates certain cells of the kidneys, called juxtaglomerular
cells, to secrete the enzyme renin.
✓ The level of renin in the blood increases.
✓ Renin converts angiotensinogen , a plasma protein produced by the liver, into
angiotensin I.
✓ Blood containing increased levels of angiotensin I circulates in the body.
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✓ As blood flows through capillaries, particularly those of the lungs, the enzyme
angiotensinconverting enzyme (ACE) converts angiotensin I into the hormone
angiotensin II.
✓ Blood level of angiotensin II increases.
✓ Angiotensin II stimulates the adrenal cortex to secretealdosterone.
✓ Blood containing increased levels of aldosterone circulates tothe kidneys.
✓ In the kidneys, aldosterone increases reabsorption of Na_,which in turn causes
reabsorption of water by osmosis. As a result, less water is lost in the urine. Aldosterone
also stimulates the kidneys to increase secretion of K+and H+ into the urine.
✓ 3 With increased water reabsorption by the kidneys, blood volume increases.
✓ 4 As blood volume increases, blood pressure increases to normal.
✓ Angiotensin II also stimulates contraction of smooth muscle in the walls of arterioles.
The resulting vasoconstriction of the arterioles increases blood pressure and thus helps
raise blood pressure to normal.
✓ Besides angiotensin II, a second stimulator of aldosterone secretion is an increase in the
K_concentration of blood (or interstitial fluid). A decrease in the blood K_ level has
the opposite effect.
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Glucocorticoids

The glucocorticoids, which regulate metabolism and resistance to stress, include cortisol (
hydrocortisone), corticosterone and cortisone. Of these three hormones secreted by the zona
fasciculata,

cortisol is the most abundant, accounting for about 95% of glucocorticoid activity.

Glucocorticoids have the following effects

1. Protein breakdown. Glucocorticoids increase the rate of protein breakdown, mainly

in muscle fibers, and thus increase the liberation of amino acids into the bloodstream.
The amino acids may be used by body cells for synthesis of new proteins or for ATP
production.
2. Glucose formation. On stimulation by glucocorticoids, liver cells may convert certain
amino acids or lactic acid to glucose, which neurons and other cells can use for ATP
production. Such conversion of a substance other than glycogen or another
monosaccharide into glucose is called gluconeogenesis
3. Lipolysis. Glucocorticoids stimulate lipolysis , the breakdown of triglycerides and
release of fatty acids from adipose tissue into the blood.
4. Resistance to stress. Glucocorticoids work in many ways to provide resistance to
stress. The additional glucose supplied by the liver cells provides tissues with a ready
source of ATP to combat a range of stresses, including exercise, fasting, fright,
temperature extremes, high altitude, bleeding, infection, surgery, trauma
5. Anti-inflammatory effects. Glucocorticoids inhibit white blood cells that participate
in inflammatory responses. glucocorticoids also retard tissue repair, and as a result,
they slow wound healing. Although high doses can cause severe mental disturbances,
glucocorticoids are very useful in the treatment of chronic inflammatory disorders
such as rheumatoid arthritis.
6. Depression of immune responses. High doses of glucocorticoids depress immune
responses. For this reason, glucocorticoids are prescribed for organ transplant
recipients to retard tissue rejection by the immune system.
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Androgens
✓ In both males and females, the adrenal cortex secretes small amounts of weak
androgens. The major androgen secreted by the adrenal gland is
dehydroepiandrosterone (DHEA) .
✓ After puberty in males, the androgen testosterone is also released in much greater
quantity by the testes.
✓ In females, adrenal androgens play important roles. They promote libido (sex drive)
and are converted into estrogens (feminizing sex steroids) by other body tissues.
✓ After menopause, when ovarian secretion of estrogens ceases, all female estrogens
come from conversion of adrenal androgens.
✓ Adrenal androgens also stimulate growth of axillary and pubic hair in boys and girls
and contribute to the prepubertal growth spurt. the main hormone that stimulates its
secretion is ACTH.

ADRENAL GLAND DISORDERS

Cushing’s Syndrome
Hypersecretion of cortisol by the adrenal cortex produces Cushing’s syndrome
Causes include a tumor of the adrenal gland that secretes cortisol, or a tumor elsewhere that
secretes adrenocorticotropic hormone (ACTH), which in turn stimulates excessive secretion of
cortisol.
The condition is characterized by breakdown of muscle proteins and redistribution of body fat,
resulting in spindly arms and legs accompanied by a rounded “moon face,” “buffalo hump” on
the back, and pendulous (hanging) abdomen.

Addison’s Disease
Hyposecretion of glucocorticoids and aldosterone causes Addison’s disease (chronic
adrenocortical insufficiency).
The majority of cases are autoimmune disorders in which antibodies cause adrenal cortex
destruction or block binding of ACTH to its receptors
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ENDOCRINE FUNCTIONS OF PANCREAS

The pancreas is both an endocrine gland and an exocrine gland. flattened organ that measures
about 12.5–15 cm (5–6 in.) in length, the pancreas is located in the curve of the duodenum, the
first part of the small intestine, and consists of a head, a body, and a tail
Roughly 99% of the exocrine cells of the pancreas are arranged in clusters called acini. The
acini produce digestive enzymes which flow into the gastrointestinal tract through a network
of ducts. Scattered among the exocrine acini are 1–2 million tiny clusters of endocrine tissue
called pancreatic islets or islets of Langerhans

Endocrine function of pancreas is performed by the islets of Langerhans. Human pancreas

contains about 1 to 2 million islets.
Islets of Langerhans consist of four types of
cells:
1. A cells or α-cells, which secrete glucagon
2. B cells or β-cells, which secrete insulin
3. D cells or δ-cells, which secrete somatostatin
4. F cells or PP cells, which secrete pancreatic
polypeptide

Regulation of Glucagon and Insulin Secretion

1. Low blood glucose level (hypoglycemia) stimulates

secretion of glucagon from alpha cells of the
pancreatic islets.
2. Glucagon acts on hepatocytes (liver cells) to
accelerate the conversion of glycogen into glucose
(glycogenolysis) and to promote formation of glucose
from lactic acid and certain amino acids
(gluconeogenesis).
3. As a result, hepatocytes release glucose into the
blood more rapidly, and blood glucose level rises. If
blood glucose continues to rise, high blood glucose
level (hyperglycemia) inhibits release of glucagon
(negative feedback).
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✓ High blood glucose (hyperglycemia) stimulates secretion of insulin by beta cells of the
pancreatic islets.
✓ Insulin acts on various cells in the body to accelerate facilitated diffusion of glucose
into cells; to speed conversion of glucose into glycogen (glycogenesis); to increase
uptake of amino acids by cells and to increase protein synthesis; to speed synthesis of
fatty acids (lipogenesis); to slow the conversion of glycogen to glucose
(glycogenolysis); and to slow the formation of glucose from lactic acid and amino acids
(gluconeogenesis).
✓ As a result, blood glucose level falls.
✓ If blood glucose level drops below normal, low blood glucose inhibits release of insulin
(negative feedback) and stimulates release of glucagon.

DISORDERS OF PANCREAS
Diabetes mellitus is a metabolic disorder characterized by high blood glucose level,
associated with other manifestations. ‘Diabetes’ means ‘polyuria’ and ‘mellitus’ means
‘honey’. The name ‘diabetes mellitus’was coined by Thomas Willis, who discovered
sweetness of urine from diabetics in 1675.

TYPES OF DIABETES MELLITUS

1. Type I Diabetes Mellitus- Type I diabetes mellitus is due to deficiency of
insulinbecause of destruction of β-cells in islets of Langerhans. This type of diabetes
mellitus may occur at any age of life. But, it usually occurs before 40 years of age and
the persons affected by this require insulin injection. So it is also called insulin-
dependent diabetes mellitus (IDDM). When it develops at infancy or childhood, it is
called juvenile diabetes.

Causes of type I diabetes mellitus

1. Degeneration of β-cells in the islets of Langerhans of pancreas
2. Destruction of β-cells by viral infection
3. Congenital disorder of β-cells
4. Destruction of β-cells during autoimmune diseases. It is due to the development of
antibodies against β-cells
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E ENDOCRINE SYSTEM

2. Type II Diabetes Mellitus- Type II diabetes mellitus is due to insulin resistance

(failure of insulin receptors to give response to insulin). So, the body is unable to use
insulin. About 90% of diabetic patients have type II diabetes mellitus. It usually occurs
after 40 years. Only some forms of Type II diabetes require insulin. In most cases, it
can be controlled by oral hypoglycemic drugs. So it is also called non insulin
dependent diabetes mellitus (NIDDM).

Causes for type II diabetes mellitus

In this type of diabetes, the structure and function of β-cells and blood level of insulin are
normal. But insulin receptors may be less, absent or abnormal, resulting in insulin resistance.
Common causes of insulin resistance
• Genetic disorders (significant factors causing type II diabetes mellitus)
• Lifestyle changes such as bad eating habits and physical inactivity, leading to obesity
• Stress.
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E ENDOCRINE SYSTEM

GONADS
✓ Gonads are the organs that produce gametes—sperm in males and oocytes in females
✓ The ovaries, paired oval bodies located in the female pelvic cavity, produce several
steroid hormones including estrogens and progesterone
✓ Along with FSH and LH from the anterior pituitary, regulate the menstrual cycle,
maintain pregnancy, and prepare the mammary glands for lactation. They also promote
enlargement of the breasts and widening of the hips at puberty
✓ The ovaries also produce inhibin, a protein hormone that inhibits secretion of follicle-
stimulating hormone (FSH).
✓ During pregnancy, the ovaries and placenta produce hormone called relaxin (RLX),
which increases
the flexibility of the pubic symphysis during pregnancy and
helps dilate the uterine cervix during labor and delivery. These actions help ease the
baby’s passage by enlarging the birth canal
✓ The male gonads, the testes, are oval glands that lie in the scrotum. The main hormone
produced and secreted by the testes is testosterone, an androgen or male sex hormone.
✓ Testosterone regulates production of sperm, and stimulates the development and
maintenance of male secondary sex characteristics, such as beard growth and deepening
of the voice.

IMPORTANT QUESTIONS
1. Write the hormones secreted by pituitary gland mention their functions - 10M/5M
2. Write the signs and symptoms of addisons diseases----2M
3. Functions of ADH and oxytocin/ functions of hormones of neurohypophysis -2M
4. Define diabetes mellitus-------2M
5. Define thyrotoxicosis and cretinism --------2M
6. Write the functions of hormones of neurohypophysis --------5M
7. Define acromegaly and gigantism --------2M
8. Write the functions of insulin and glucagon-------5M
9. Name gonadotropins and write their functions --------2M
10. what is hyperthyroidism -------2m
11. Functions of thyroxine --------------2m

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