• t
tf
ENDOCIINE
SYSTBM _
. .d
II

341
m
ENDOCRINE SYSTEM
l . Endocrine system includes the group of glands that secrete hormones,.
2. The endocrine glands secrete their products into the extra-cellular' ·
space around the secretory cells rather than into theducts.
3• The secretion then d1ffiises int~ e capillaries and is carried away by
the blood. · ·
4. In the body, some glands are entirely endocrine in nature. In addition
to these glands, several organs contain endocrine tissue it them.
5. The branch of science that deals with the study of structure and
function of endocrine glands is called as endocrinolo .
6. The ~rvous§}'.;Stem and endocrine s ste • ncti9ns in coordination
with one another to maintain the homeostasis of all body system.
Hypothalamus
Adrenal gland _ _ .,
Pancreas
Pituitary gland
Thyroid gland
Thymus gland
,...__ Ovary
Testes

/1wtolflY & /-'/,ysioloRY for Para-Medic:s
J4l
Effects
-- hows the following effects. They are:
ThC' cmh>crl11c system 8
·
f
p fl n•gulnh'S
11
,.. chemicul composition and volume o the extra-cellular
'- lh1id.
'- LI) 11 Tclps in r"bn,htlion of mctnbolism and cn ~r~ balance.
LIi) ~
1
rclulal<'S ron1raclion of smool.h and ca,doac muscle fibers and
" secretion by gkinds. . .
Iv) 11 ma1
11
I1ti
11
, hom
0
costasls desp•le em crgency, en v1ronmental
disrnptions such as infection, trauma, emotional stress, dehydration,
slflrvntion, haemorrhage and temperature extremes.
vY(ltcgulates cerlain activities of the imm~ne system.
vi) II play a role" in the smooth; sequential integratiOn of growth and
development.
vii) lt contributes to the basic processes of reproduction, including gamete
production, fertilization, nourishment of the embryo and feotus,
delivery and nourishment of the new born.
Some endocrine glands and the organs with endocrine tissue:
1. Piluilary gland
2. Hypothalamus
3. Thyroid gland
4. Para thyroid gland
5. Adrenal gland
6. Pineal body
7. Pancreas
8. Thyn1us
9. Ovaries (in females)
IO. Testis (in males)
IPituitary gland I
l. Pituitary gland is called
h as master endocrin z d b
ormones secreted by th . . - e g an ecause the
glands. e pituitary gland controls the other endoctine
2. Pitui~'l.fy gland .s a pea-sized land .
It weighs about 50'0 m g measunng about 1.3 cm in diameter.
3. Pituitary gland is situa~d in the .
attached lo tJ1e hypotha1 ~lla turcua of the sphenoid bone. It is
infandibulum. amus Y a stock like structure called the
4. The pituitary gland is d' 'd d .
.
iv1 e mto tw
regions. They a.re: o anatomical and functional
J Anterior pituitary l ( ·
2. Posterior pituitarygg:1
!(anteri~r lobe)
n posterior lobe)

Endocrine System 343
5
· The anterior pituitary gland is about 750/o of the total weigh~ 0 ~
the
gland. The remaining portion of the gland is the posterior pitmtary
gland.
6· A 3_
rd
region called the par.r intermedia (intermediate lobe) at~ophies
dl~.nng feotal development and is small in adults. Som.e of its cells
migrate into the anterior pituitary.
Anterior lobe
Posterior lobe
Sella turcica
IAnterior pituitary gland I
1. The anterior pituitary gland is also called as adenohypophysis.'
2. The anterior pituitary gland secretes several hormones that•
regulate a wide range of bodily activities starting from growtl to
reproduction.
3. Release of hormones by anterior pituitary is stimulated by releasing
hormones and suppressed by inhibiting hormones from hypothalamus.
4. The principle hormones released by the anterior pituitary glarid are:
i) Growth hormone [GH]
ii) Thyroid stimulating hormone [TSH]
iii) Adrenocorticotrophic hormone [ACTH]
iv) Follicle stimulating hormone [FSH]
v) Luteinizing hormone [LH]
vi) Melanocyte stimulating.hormone [MSH]
vii) Prolactin [PRL]
!Growth hormone [GH] I
1. Growth hormone [GH] or human Growth hormone [hGH] is also
known as somatotropin and is secreted by the acidophil cells.
2. Growth hormone is the most abundant hormone synthesised by the
anterior pituitary.
3. Growth hormo~e stimulates growth and division of most body cells
especially cells m bones and skeletal muscle tissue.

344
Anatomy & Physiology for Para-Medics
4 G ti l Causes cells to grow and multiply by directly
. row·1 1onnone
· · tJ t at which amino-acids enter cells and are used to
mcreasmg 1e ra c
synthesize proteins.
5. In addition to tJ,e growth of the cells, lhe growth hormone shows
effects on tl1e metabolism.
6. They are: . . .
i) It stimulates protein synthesis and inh1b1ts ~rotem.bre~k down.
ii) It stimulates lipolysis, the break down of tnglycendes mto .fatty
acids and glycerol. .
iii) It retards the use of blood sugar for ATP product10n.
7. By regulating carbohydrate, protein and lipid metabolism, growth
hormone promotes growth of the body.
n'iGrowth hormone decreases utilization by the cells, decreases glucose
'Q up-take by the cells and it accelerates the rate of conversion of liver
glycogen to glucose which leads to increased blood glucose levels.
9. The secretion of growth hormone from the anterior pituitary is
controlled by two hormones. They are:
1. Growth hormone releasing hormone (GHRH)
2. Growth hormone inhibiting hormone (GHIH)
10. Hypoglycemia decreased fatty acids and increased amino acids in
the blood, deep sleep, and increased activity of the sympathetic
division causes release ofGHRH by the hypothalamus which in turn
causes release of GH.
IClinical significance I
1. Hypopituitarism may be due to atrophy of ill development of the
acidophil cells in infants and children and causes retardation ofskeletal
growth which leads to dwarfism.
2. Hyperpituitarism may be due to acidophil cell tumour in the young
and increases skeletal growth which leads to gigantism.
3. Hyperpituitarism in the adults leads to increase in thickness of lower
jaw, hands and feet producing gorilla like appearance called
acromegaly.
IThyroid stimulating hormone [TSH] I
1. Thyroid stimulating hormone is also called as thyrotropin secreted ·
by basophil cells. It controls growth and activity of the thyroid
gland.
2. It stimulates the synthesis and secretion of T3
(triiodothyronine) and
T4 (thyroxin) by the thyroid gland.
3. T.hP sP.cretion of the TSH is controlled by thyroid releasing hormone
(TRH) from the hypothalamus.

l:..'ndocrine S
· ystl'm
4
· ~ elease of TRH depcndR on th~ blond levPIRof TRI I, T.,•'I'.. hl,MI
g ucosc level a.nd body's rnetaboltc ral1· ot.c.
[Adrenocorttcotrophic hormone (ACTH]]
1· Adre~ocorticotrophic hormone is Rccr-cted by the bwwphil c,.dl1', Th,!
secretion is under the control oft.he coretcofro/Jin rele(J.fing/zormone(CRJ J)
from hypothalamus.
2· Stress relate-
d stimuli also stimulate the production of ACrH. It helps
in the growth and development of the adrenal cortex.
3. Adrenocorticotrophic hormone controls the production and 8ccrction
of hormones by the cortex of the adrenal glands.
·IFolllcle -stimulating hormone (FSHj I
1. Foliicle stimulating hormone is secreted by I.he basophil cellR.
2. In females, follicle stimulating hormone is transported from the
anterior pituitary by the blood to the ovaries.
3. Follicle stimulating hormone initiates the development of egg
containing follicles each month.
4. FSH stimulates follicular cells to secrete estrogens.
5. In males, FSH stimulates sperm production in the testes. ,
6. The gonadotropin releasing hormone (G~RH) from hypothalamus
stimulates release of FSH.
ILutelniztng hormone (lll}I
.
1. Luteinizing hormone is secreted by the basophil cel1s. The Secretion
of Iuteinizing hormone is also controlled by GnRH.
2. In females, the luteinizing hormone together with FSH stimul~s
estrogen secretion by the ovarian cells. ,
3. This brings about the release of a secondary oocyte from the ovary
by a process called ovulation.
4_ Luteinizing hormone also stimulfates formationbofththe corpus luteum
in the ovary and the secretion o progesterone y e corpus luteum.
In males, the luteinizing hormone stimulates the interstitial cells in
5
· the testes to develop and ~e~r~te large amo~ts of testosterone.
6
_ Because of this reason luteiruzmg hormone 18 also called as inttrstitia.l
cell stbnulating hormone (ICSH).
(!delanocyte stimulating hormone {MSH] I
Melanocyte stimulating hormone is secreted by the basophil cells
1. and acidophil cells. . . .
Melanocyte stim~atin~ hormone in.creases the ~kin pigmentation by
2· stiJ11Ulating the dispersion of melarun granules m melanocytes.

346
Anatomy & Physiology for Para-Medics
3
. The hormone MSH releasing hormone (MRH) promotes release of
4_ ~h:~ormone MSH inhibiting hormone (MIH) suppresses release of
MSH.
[Prolactin [PRL] I
1. Prolactin or lactogenic hormone is secr~t~~ by the acid?p~l cell~.
2. Prolactin together with other hormones 1mtiates and mamtains milk
secretion by the mammary glands.
3. The hormone prolactin inhibiting hormone (PIH) from hypothalamus
inhibits the secretion of prolactin.
4. The hormone prolactin releasing hormone (PRH) from hypothalamus
promotes the secretion of prolactin.
IPosterior pituitary gland I
1. Although the posterior pituitary gland does not synthesize hormones,
it stores and releases two hormones.
2. The two hormones are
1. Oxytocin [OT]
2. Vasopressin
3. After the production of hormones by the neurosecretory cells of
hypothalamus, they are packed into the secretory vesicles.
4. Then they are released from the axon terminals of the posterior
pituitary gland.
IOxytocin [OTJI
~ - 1. Oxytocin is produced by the neurosecretory cells of hypothalamus.
2. During and after the delivery of the baby, oxytocin has two target
tissues. They are the uterus and breast of the mother.
3. During delivery, it enhances the contraction of smooth muscle cells
in the wall of the uterus.
4. After delivery, it stimulates milk ejection from the mammary
glands in response to the mechanical stimulus provided by a suckling
infant.
5. ·The function of oxytocin in males and non pregnants is not clear.
6. During delivery, oxytocin is released in large quantities. When labour
contractions begin the baby's head stretches the cervix of the uterus.
7. Through the stretch receptors, the sensations reach the hypothalamus
that lead to the stimulation of posterior pituitary to release oxytocin
into blood.
8. With the birth, the cycle is broken because the cervical distension
suddenly lessens.

Endocrine System
347
9
· ~n the process of milk eiection the sucklinu stimulates the receptors
m the . l J ' b .
h nipp e that generates sensory impulses that are transrmtted to
10. T~:
th
xytal~us causing release of oxytocin. d h l d I
0 cm stimulates the smooth muscle cells aroun t e g an u ar
ce~s and ducts to contract and eject milk. This sequence is called as
· milk ejection.
11· Oxytocin facilitates the transport of sperms in the female genital
tract.
I Antidiuretic hormone (ADH] I:
1. Antidiuretic hormone (ADH) is also called as vasopressin because it
is having antidiuretic effect.
2. Vasopressin is released in response to stress and also in response to
dehydration.
3• Antidiuretic hormone is produced by the neurosecretory cells of
hypothalamus. .
4. Antidiuretic hormone increases the re-absorption of water by the
nephron and thus reduces the volume of urine formation.
5. It reduces the chloride absorption and thus increases chloride loss.
6. It causes the contraction of all the plain muscles of the body except
those of heart and uterus.
7. Antidiuretic hormone causes contraction of capillaries, generally it
raises blood pressure.
8. Heart rate in reflexive action is reduced due to high blood
pressure.
g. H yperpnoea, with occasional apnoea is seen due to changes in blood
pressure which reflexively act on the respiratory center.
10. The intestinal muscles contract and movement of stoma-
ch,
small intestine and large intestine increases due to the effect of
vasopressin.
l l. Pain, stress, trauma, anxietyh, acetylcho
1
line, nicotine, drugs like
morphine and some anest etics stimu ates the secretion of the
hormone.
Alcohol inhibits the secretion of this hormone thereby increasing
the urine output.
12.
Disorders of pituitary gland
IGIGANTISMI
Gigantism is caused by the hyper activity of anterior pituitary in
1. 1
oung peop e.
imscondition occurs because of particular rise of GH before fusion
2· f • hysel cartilages of long bones.
0 ep1p

348 Anatomy & Physiology for Para-Medics
3. The persons will be very taJl about 2 - 2·5 meters.
4. The muscles and viscera are proportionally large.
5. Basal metabolic rate increases and sweating increases.
6. The other endocrine glands such as thyroid, adrenal cortex, gonads,
thyn1us etc. Show hyperactivity.
IACROMf:GALYI
l. Acromegaly is caused by the hyper activity of anterior pituitary in
adult people.
2. This condition occurs because of particular rise of GH after fusion of
epiphysel cartilages of long bones.
3. The bones become abnormally thick due to ossification ofperiosteum
and there is thickening of the soft tissues.
4. Overgrowth of two jaws, supraorbital ridges etc is seen.
5. Hands and feet enlarge, bowing of spine (kyphosis) is seen.
6. Because of this reason, the person assumes gorilla, like appearance.
7. The subcutaneous tissue of the hands, feet, scalp, nose, lips and the
skin increases in amount, producing deep furrows. Tongue is also
enlarged.
8. Hyperglycaemia reduced sugar tolerance and in some cases,
glycosuria also seen.
9. Basal metabolic rate increases and sweating also increases.
10. Organs concerned with metabolism such as liver, heart, lungs,
kidneys, pancreas, spleen etc are enlarged.
11. Other endocrine glands such as thyroid, adrenal cortex, gonads,
thymus etc show hyperactivity.
12. The person also shows many other manifestations like papilledema,
rhinorrhoea, deepening of voice, visual disturbances, drowsiness,
lethargy, cutaneous pigmentation and hypertension.
13. The males show diminished libido and some times impotence.
14. The females show amenorrhoea, development of sterility, failure of
breast development.
!DW
ARFISM I
Dwarfism is caused by hypo activity of the anterior pituitary in the
young people.
It is of 3 types:
i) Lorain - Levy type
ii) Brissaud type
iii) Mixed type.

Endocrine System
349
Lorain - Levy type (infantilism)
~- 8tunted growth is seen. The adult about 2.5 - 3 feet high.
· Sex organs do not grow. Secondary sexual characters are not seen.
Hence an adult man resembles a normal child.
3. The intelligence is normal and proportional to age.
4. Metabolism is normal.
Brissaud type: The condition is same as Lorain - levy type. In addition
to that excess deposition of fat in the body, round chubby face, no beard, no
mustaches, sleepy and slothful nature.
Mixed type:
I. There is a mixed histological nature and combined clinical
manifestations and may be called dyspituitarism.
2• The subject may be fatty and hairless, may have large accessory nasal
sinuses, prominent supra-orbital ridges.
fCUSHI~G~
S '
DISEASE.
f
1. This disease occurs because of hyper activity of basophil cells of the
pituitary gland.
2. In this condition, there is excessive deposition of fat over the
supracondylar fossae, which gives rounded or moon-face in a well
. developed case.
3. Fatty deposition also takes place in back of neck and abdomen.
Extremities are usually spared.
4. Fatty deposits are tender and painful, purplish striae are seen over
the abdomen, thighs etc. This is due to loss ofprotein matrix. Women
are affected 4 times more than men.
5. In males, excessive hair growth (hirsutism) is seen. In females,
masculinisation with growth of beard, mustaches etc is seen.
6. Asthenia and wasting ofmuscles ofthe limbs and obesity of the trunk
is seen.
7. Osteoporosis ofbones due to decalcification and loss ofprotein matrix
takes place.
8. In few patients, hypertension is seen.
g. The person also has mental derangement.
lO. In males, impotency with atrophy oftestis and in females amenorrhoea,
sterility occurs. .
11. Hyperglycaemi~ and glyc~s~a _are seen. .
12. Retention ofsodium and diminution ofpotassmm levels in the plasma
take place. .
3 Eosinopenia, Lympocytoperua and Polycythaemia are seen.
!4: Increased excretion of 17 - Oxogenic steroids and 17 _ Hydroxy
corticosteroids occurs.

350 Anatomy & Physiology for Para-Medics
IFROHLICH'S SYNDROME I
This condition is also called as adiposogenital dystrophy. It shows the
features due to deficiency ofGH, FSH, LH. The features are as follows:
In children:
a) Stunted growth
b) Idiotic
c) Sexual infantilism
d) Generalised obesity
In males (adults):
1. Adipose of feminine distribution.
2. Mental disposition and appearance resemble females.
3. Degeneration of sex.
4. Hands and feet are small and pretty, fingers delicate and tapering.
5. Skin of face and body is smooth and hairless.
In females (adults):
I. Extreme adiposity.
2. Degeneration of sex.
IDIABETES INSIPIDUSI
1. The Diabetes insipidus is caused due to the deficiency ofthe hormone
ADH.
2. The deficiency of ADH may occur because of damage of
hypothalamus. Example: trauma, twnour, encephalitis etc~ ,..-
3. Occasionally, the renal tubulesmaynotrespond bythe action-OfADH.
4. This leads to excretion of excessive amounts of dilute urine; which
leads to dehydration results injolydipisia.
5. Water balance is disturbed unless fluid intake is greatly increased to
compensate for excess losses.
IHypothalamusI
1. Hypothalamus is the smaller region of the brain present below the
two lobes of the thalamus.
2. Hypothalamus is the major integrating link between the nervous
system and endocrine system.
3. Hypothalamus receives input from several other regions ofthe brain.
It also receives sensory signals from internal organs and perhaps from
the visceral system.

Endocrine System
351
4· Painful, stressful and emotional experiences all cause changes in
hypothalamic activity.
5· In turn, the hypothalamus controls the autonomic nervous SYst~m
and regulates the body temperature, thirst, hunger, sexual behaVIor
and defensive reactions such as fear and rage.
6. Hypothalamus not only acts as a important regulatory c~nter of
nervous system, it also secretes several hormones that regulate the
secretions from pituitary gland.
7. Hypothalamus secretes the releasing hormones and inhibiting
hormones which influence the pituitary gland.
8. The hormones released by the Hypothalamus are:
1. GHRH - Growth Hormone Releasing Hormone
2. G HIH - Growth Hormone Inhibiting Hormone
3. TRH - Thyroid Releasing Hormone
4. CRH - Corticotrophin Releasing Hormone
5. PRH - Prolactin Releasing Hormone
6. PIH - Prolactin Inhibiting Hormone
7. LHRH - Luteinizing Hormone R~leasing Hormone
8. GnRH - Gonadotropin Releasing Hormone
Right lobe of
the thyroid
Isthmus
Thyroid gland
,Anterior view,
Left lobe of
the thyroid
Trachea
1. The thyroid gland is situated in the neck in front of the larynx d
trachea at the level of5th
, 6th
, and 7th
cervical vertebra and 1• th ~
orac1c
vertebra.
2. Itis a highly vascular gland that weighs about 25gms and is surrounded
by a fibrous capsule.

3S2
I I :.-' ~ ✓
A11atomy & Physiology for Para-Medics
3. Thyroid gland has 2 lobes: tl1e right lateral lobe a.nd left lateral lobe
lie one on either side of the trn.chea. . .
4. The 2 lobes are connected by a mass of tissue called an isthmus,
which lies in front of the b:achea. .
5. :rviicroscopically each lobe is having spheticaJ sacTsc
halled !:Jroid[ollicles._
The thyroid follicles consist of 2 types of cells. ey are:
i) Follicular cells
ii) Para follicular cells or 'C' cells .
6. The rna>dn1urn area is occupied by the follicular cells. Under the
influence of TSH, the follicular cells secretes T3 (triiodothyronine)
and T4
(thyroxin).
7. The 'C ' cells secretes calcitonin, wpich influences calcium
homoeostasis.
8. The thyroid gland is the only endocrine gland that stores its secretory
product in large quantities. Normally about 100 days supply.
9. Out ofT3
and T4
, normally T4
is secreted in greater quantity than T3•
But T3
is several times more potent and more active than T4•
IO. Because of this, most T4
is converted into T3 by removing one
iodine.
IFunctions I
I. Calorigenic: Thyroid hormones accelerate energy production,
oxygen up take and basal metabolic rate (BM.R).
2. Carbohydrate metabolism:
i) Thyroid hormones stimulate absorption of glucose from the
intestine.
ii) Mobilises glycogen from liver and heart~
iii) Promotes gluconeogenesis.
iv) Causes hyperglycaemia.
v) Reduces sugar tolerance.
3. Protein metabolism:
i) In moderate concentrations, the thyroid hormones have an anabolic
effect.
ii) In high concentration, negative nitrogen balance is observed and
protein synthesis is depressed.
4. Lipid metabolism:
i) The concentration of most of the lipids of the serum especially
.. cholester~l varies inversely with the level of thyroid activity.
n) The thyr01d hormones increases both synthesis and the catabolism
... of cholesterol and other lipids.
m) In hypothyroidism, the balance between the two is
~rupted, which leads to less lipid catabolism, hence serum lipids
mcrease.

Endocrine System 353
1· C_
alcium and phosphate metabolism:
-~
) They remove Ca and P from the bones leading to osteoporosis.
u) Causing no rise of serum calcium.
iii) Increased calcium loss both in feces and urine.
2. Kidneys:
i) Increased nitrogen excretion.
ii) Increased urine volume along with increased elimination of salt
probably due to rise in general metabolism.
iii) Increases the excretion of creatinf N2
3 . Growth and m etamorphosis~:,_____
i) Thyroid hormones are essential for growth and metamorphosis.
ii) Decreased levels of thyroid hormones lead to retardation of
growth and metamorphosis.
4. Mammary gland: Thyroid hormones increase the output and fat
content of the milk.
5. Heart rate: Thyroxin accelerates the rate of the normal as well
as the denervated heart It acts directly on the pace maker of the
heart.
6. Nerves and muscles: Thyroid hormones influence the levels and
activities of the central, peripheral and autonomous nervous systems
and of the voluntary muscles.
IHYPOTHYROIDISM I
Hypothyroidism produces
a) Cretinism (in children)
b) Myxoedema (in adults)
!CRETINISMI
I. This condition occurs due to deficiency· of thyroid secretions in
children.
2. The symptoms do not appear till after 6 months, because enough
hormones are present in mother's milk.
3. The milestones of children such as Holding up the head, Sitting,
Dentition; Closure of anterior fontanelle, Standing, Walking and
Speech etc are delayed. ·
4. Regarding Skeleton, Stunted growth, Short club-like fingers,
Deformed bones and Teeth are seen.
5. The skin is rough, thick, dry, and wrinkled. Hair scanty.
6. The face is blotted, idiotic look, thick parted lips, large protruding
tongue are present. ·
7. Saliva is dribbling. Broad nose with depressed bridge is present.
8. The abdomen is pot bellied and umbilicus often protruding.

354 Anatomy & Physiology for Para-Medics
9. The sex glands, sex organs and secondary sexual characters
retarded.
10. The patient is ,:
diocy of varying degrees, often deaf.and dumb.
11. Regarding gastro intestinal tract and metabolism the patient's
i) appetite is reduced.
ii) Motility of gastro-intestinal tract is reduced and there is often
constipation.
iii) BMR is lowered by 20 - 40 %
iv) Low body temperature is recorded
v) Irregular deposit of fat specially above the clavicle is seen.
12. Regarding blood, the following conditions are seen:
a) Low blood sugar
b) High sugar tolerance
c) High serum cholesterol
d) Low blood iodine
13. The resistance of the person is lowered. The person is susceptible to
cold, toxins and inter current infections.
14. In urine, the creatine excretion is less.
15. The carotene accumulates sufficiently to cause yellowing of the skin
but not the sclera
IMYXOEDEMA I
1. Myxoedema is also called as Gulls disease. This disease occurs 7 - 8
times more frequently in females than in males.
2. Theface, skin and body are swollen, puffy and oedematous due to
the deposition of myxomatous tissue.
3. Swelling of tongue and larynx causes hoarseness and slow slurring
speech.
4. Irregular deposit of fat in the body takes place. Hair falls out from
axilla, pubis, head and outer third of the eyebrows.
5. Sex degenerates, impotency, amenorrhoea etc are seen.
6. Impaired mental condition, dullness, loss of memory, somnolence
etc are seen.
7. Regarding gastrointestinal tract, appetite is reduced, motility of
the gastrointestinal tract reduces and there is often constipation.
8. The basal metabolic rate is lowered by 30 - 40 %, body temperature
is also lowered.
9. The patient develops increased susceptibility for cold, body weight
increases.
10. Regarding blood
i) Low blood sugar and iodine is seen.
ii) Increased sugar tolerance is seen.
iii) Serum cholesterol rises above 300 mg per 100 ml.

Endocrine S
)'Sten,
11.
12.
iv) Secondary an .
v) Ri aerma
Th h se of plasma proteins is seen.
e ea.rt rat· . 1 . .
N· e is s ow and increased circulatory time is seen.
itrogen excretion is less in udne.
355
[GOITRE I
l . Goitre is · ,n,. . · f h
. non m1""mmatory and non neoplastic enlargement o t e
thyroid gland.
2
· In si~ple goitre, usually there are no constitutional features of hypo
function or hyper function of the gland.
3. The causes for goitre are:
A) Iodine deficiency
B) Presence of goitrogenic substances in the diet
C) Some drugs etc.
4. There may be only pressure symptoms due to enlargement of the
gland. The simple goitre may be of following types:
i) Colloid goitre
ii) Diffuse parenchymatous goitre
iii) Nodular goitre
iv) Toxic goitre ·
)colloid goitre.I
1. Colloid goitre is a deficiency disorder caused by an in adequate supply
of iodine in the diet.
2. The alveoli are distended with colloid lined by cubical or flattened
epithelial cells.
3. There is no hypertrophy or hyperplasia of the cells.
4. Use of iodised salt reduces the incidence of simple goitre.
}Diffuse parenchymatous goitre I
1. The alveoli are not distended with colloid like in the colloid goitre.
2. Toe cells lining the alveoli are of columnar type.
3. There is hypertrophy and hyperplasia of the alveolar epithelial
cells.
4. The lumens of the some of the alveoli are almost obliterated.
~odular goitreJ . .
l . This is also called as adenomatous goitre. There 1s nodular swelling of
part of the thyroid gland.
(Toste goitr~
E
nlargement of the thyroid gland along with excessive secretion of
1. .
thyroid honnones 1s seen.

356
Anatomy & Physiology for Para-Medics
Th ithelial cells undergo hypertrophy and hyperplasia.
;: To~:~ymptoms develop due to hyperthyroidism. Graves' disease is
always associated with toxic goitre.
IHokkaido goitre I
1. The deficiency of iodine may cause endemic goitre, a very high
concentration ofiodine may also cause hypothyroidism by inhibiting
iodine organification that is the Wolffchaikoffeffect.
2. This condition is also named as Hokkaido goitre because this condition
is more common in the area called Hokkaido inJapan.
3. Iodine in high doses also interferes with the release ofT4 and T3 from
the thyroid gland.
4. Parenchymal hyperplasia is very much marked and majority of
patients suffer with hypothyroidism.
IGRAVES' DISEASE I
Graves' disease is also called as Basedow1' disease or Exophthalmic goitre.
Graves' disease occurs due to excessive secretion of thyroxine. The main
features of Graves' disease as follows:
Enlarged thyroid: The hypertrophy and hyperplasia of the cells leads to
the enlargement of the thyroid gland.
Increased BMR: The basal metabolic rate increases by 50 - 1000/o, body
temperature rises.
jEye signs'
I. Protrusion of the ·eyeball with a staring look, less twinkling of the
eye-lids is called as exophthalmos.
2. Exophthalmos condition occurs due to deposition of fat in the retro-
ocular region.
3. Retraction of eyelids is caused by infiltration of fat in the levator
palpebral superioris which leads to the spasm of that muscle.·
4. Ophthalmoplegia or weakness of the external ocular muscles occurs
due to excessive deposition of fat in these muscles.
Body: Body weight decreases and fat stores depleted.
Mental oonditwn: Sharp, emotional, restless, easy fatiguability.
Skeleton: Osteoporosis is seen due to excessive loss of calcium and
phosphorus.
Skin: Soft, moist and flushed due to vasodilatation which helps in heat
loss.

Endocrine System
(Blood)
1
) Blood sugar rises, it n1ay lead to gl.ycosuriu.
U) Lowered sugar tolerance.
ill) Increased iodine content.
iv) Lowered cholesterol content.
357
Liver: Efficiency of the liver decreases and the glycogen levels reduced.
(Heart and ctrndatton I
i) Heart rate increases
U). Systolic blood pressure increases
ill) Fall in circulation time is seen.
Voluntary muscle: Fine tremor, increased ankle jerk reflex and muscle
weakness are seen in voluntary muscles. ·
Electroencephalogram: Electroencephalogram shows abnormal alpha -
wave.
Vitamins: Due to raised basal metabolic rate, vitamin requirement rises
especially for vitamin A, B and·C.
The patient is sensitive to heat and susceptible to infection.
IParathyroid gland!
Parathyroid gland
1. There are four small parathyroid glands present in the posterior
surface of each lobe of the thyroid gland.
2. One gland is present in the superior aspect and the other gland is
present in the inferior aspect ?fthe lobe of ~e thyr~id gland.
3. Microscopically the parathyroid gland contains two kinds ofepithelial
cells. The more numerous cells are called principle (chief) cells
and the other cells are oxyphil cells.
4. The principle cells are resp(~=ible for the production of the hormone
called parathyroid hormone .r.,'H) or parathormone.

358
Anatomy & Physiology for Para-Medics
IFunctions of parathyroid hormone I
1 It · es the rate of bone resorption with consequent mobilisation
. mcreas .
of calcium and phosphate.
2. Parathyroid hormone increases the blood Ca++ and Mg++ levels and
decreases phosphate levels. .
3. Parathyroid hormone directly increases renal tubular re-absorption
of calcium.
4. Parathyroid hormone increases direct renal excretion of phosphate.
5. Parathyroid hormone may increase the Ca++ absorption in the gut.
6. Parathyroid hormone may decrease the rate of Ca++ secretion by the
lactating mammary gland.
7. Parathyroid hormone may control the intra-cellular deposition of
phosphate.
8. Decreased parathyroid hormone levels leads to a disease called
tetany.
ITETANYI
1. Tetany is caused due to lowered ionic calcium in blood and in tissue
fluid.
2. The lowered ionic calcium levels may occur because of accidental
removal of parathyroid gland during thyroid surgery.
3. The patient has increased neuromuscular irritability.
4. Fall in serum calcium levels and rise of inorganic phosphate levels.
5. Excretion of calcium and phosphorus in urine gets reduced.
6. Heart rate increases. Secretion of saliva increases.
7. General convulsion is seen in children.
8. Carpopedal spasm or Trousseau's sign:
i) Elbow and wrist flexed Fingers
ii) Flexed at metacarpophalangeal joint but extended at the
interphalangeal joints
iii) Thumb in the palm and finger tips drawn together
iv) Feet extended and plantar flexed. Slightest pressure on the limbs
may elicit this.
9. Sp?8m of the glottis with inspiratory stridor is called as Laryngismus
stridulus is seen.
10. Chvostek's sign: Tapping the facial nerve near the styloid process
causes facial spasm. This is called as Chvostek's sign.
11. Increased excitability ofmotor nerve to galvanic current called Erb's
sign is seen.
12. Apart from parathyroi~ deficiency, hypocalcaemia tetany is also found
in the conditions like Alkalaemia, Renal failure, Rickets, Impaired
absorption of calcium, Increase in alkaline phosphate levels.

Endocrine System 359
JAdrenalgland I
1. The adrenal glands are also called as supra-renal glands because
they are situated on the upper pole of both kidneys. They are 2 in
number.
2. The Adre nal glands are enclosed in the renal fascia. Each gland
measures about 4 cm long and 3 cm thick. It is also highly vascular.
3. Structurally and functionally, the gland is differentiated into 2 regions.
They are
1. Adrenal cortex
2. Adrenal medulla
IAdrenal cortexI
1. The adrenal cortex is the outer-most area of the adrenal gland.
2. The adrenal cortex is subdivided into 3 Zones which secretes
different groups of steroid hormones.
IZona glomernlosaJ
1. Zona glomerulosa is the outerzonewhich secretes a group ofhormones
called mineralocorlicoids.
2. Aldosterone is the main mineralocorticoids. The functions are
associated with the maintenance of water and electrolyte balance in
the body.
3. It stimulates the re-absorption of Na+ by the renal tubules and
excretion of K+in the urine.
4. By means of sodium absorption and water retention, aldosterone
regulates the blood volume and blood pressure.
5. Increased K+ levels and Angiotensin stimulate the release of
aldosterone.
IZona fasciculata I
l. Zona fasciculata is the middle zanewhich secretes a group ofhormones
called glucocorticoids.
2. Cortisol, Corticosterone and Cortisone are the main glucocorticoids.
Cortisol is the most abundant and is responsible for 95% of
glucocorticoid activity.
3. The glucocorticoids together with other hormones promote normal
metabolism.
4. They increase the rate at which proteins are catabolized and amino
acids are removed from the cells. Glucocorticoids provide resistance
to stress.
5. Their role is to make sure en~ug~ that_AT~ in available. They are
responsible for gluconeogenes1s, hpolys1s, stimulates the breakdown

360
Anatomy & Physiology for Para-11 d'
m.e ICS
of proteins.
6. They also promote the absorption of sodium and water form the
renal tubules.
7. Increased concentrations of the glucocorticoids decreases cellular
protective reactions.
IZona reticularis I
1. Zona reticularis is the inner zone which secretes a group of hormones
called gonadocorticoids.
2. The adrenal cortex secretes both male and female gonadocorticoids.
They are Estrogens and Androgens.
3. Estrogens are several closely related female sex hormones that are
also produced by the ovaries and placenta.
4. Androgens are the hormones that exert masculinizing effects.
An important androgen called testosterone is produced by the
testes.
5. The amount ofsex hormones secreted by normal adult male is usually
so low that their effects are insignificant.
6. In females, adrenal androgens contribute to sex derive (libido) and
other sexual behavior.
7. They also can be converted into estrogens which is significant when
ovarian estrogen secretion diminishes during menopause.
IAdrenal medulla I
1. Adrenal medulla is the area present in the inner aspect of the adrenal
cortex.
2. The adrenal medulla consists of hormone producing cells called
chroma/Jin cellr.
3. The chromaffin cells receive direct innervation from preganglionic
neurons of the sympathetic division of the autonomic nervous
system.
4. The two principle hormones synthesised by the adrenal medulla are
Epinephrine and Norepinephrine. They· are also called as
Adrenaline and Noradrenaline respectively.
5. Epinephrine constitutes about 800/o of the total secretion ofthe gland.
Both hormones are sympathomimetic. This means the action is similar
to sympathetic division of autonomic nervous system.
6. To a large extent they are responsible for fight or flight response.
Under stress, the output of these hormones increases.
7. The hormones show following effects:
i) Increases blood pressure by increasing heart rate, force of
contraction and constricting the blood vessels.
ii) They accelerate the rate ofrespiration, dilatation ofthe respiratory

Endocrine System 361
passages.
iii)
Decreases the rate of digestion.
iv) Increases the efficiency of muscle contraction.
;)) ~creases blood sugar levels and stimulate cellular metabolism.
Dilatation of pupil.
IADDISON'S DISEASE I
1· Thi~ disease occurs due to chronic insufficiency of adrenal secretions
particularly cortical secretions.
2- ~ddison's disease occurs usually due to tuber~ulosis of the gland
mvolving both cortex and medulla.
3. But the effects are mainly due to insufficient secretion of cortisol and
aldostero~.
fClinical features f
I. Muscular weakness and easy fatiguability: They are due to
loss of sodium chloride and defective power of glycogen
formation.
2. Vomiting, anorexia, and gastrointestinal disturbances.
3. Low blood pressure.
4. Bronze pigmentation of the skin is seen especially in the exposed
areas·and mucous membranes.
5. Low BMR and sub normal temperature is seen.
6. Ionic balance is disturbed.
7. Decreased blood volume and haemoconcentration will take place.
8. Disturbances in the glucose metabolism:
i) Absorption of sugar from the small intestine is slowed down.
ii) Glycogenesis and gluconeogenesis in the liver are depressed.
iii) Hypoglycaemia
g_ Deficiency of kidney functions: Glomerular filtration rate is
decreased which leads to low urine volume, retention of nitrogenous
waste products.
JO. Absorption of the lipids from the intestine and lipid metabolism is
diminished.
Restless, in50mnia, lack of mental concentration are seen.
l l. Depression of sexual function is seen.
12.
fuBYPEJIFUNCffON OF ADRENAL CORTEX I
H r function of adrenal cortex causes 3 conditions. They are:
~ -.!:!rung's syndrome
1. v~ .
2. flyperaldosterorusm

362
Anatomy &Physiology for Para-Medics
3. Adrenogenital syndrome
ICUSHING'S SYNDROME I
1. Cushing's syndrom~ is found in adrenal tu?1our or adrenal
hyperplasia and there is excessive secretion of cortisol.
2. Pituitary tumours causing excess secretion of ACTH may be the
reason of this syndrome.
IClinical features I
1. Increased deposition offat on the trunk face, pad offat on the back of
neck and abdomen is seen.
2. The fatty deposits are painful. The skin is bruised easily and shows
purple striae usually over the abdomen and thighs in females.
3. In males, excessive hair grows. This condition is called as hirsutism
and impotency with atrophy of testis is seen.
4. In females, masculitiisation with growth of beard and mustaches is
seen, and amenorrhoea, sterility is seen.
5. Asthenia and wasting of muscles of the limbs are seen.
6. Wounds heal properly and minor injuries cause bruises and echimosis.
7. Osteoporosis of bones takes place due to decalcification and loss of
protein matrix.
8. Hypertension is seen.
9. Mental derangement occurs.
10. Hyperglycaemia and insulin resistant diabetes with glycosuria occurs.
11. Retention of sodium and diminution of potassium level takes place
in the plasma.
12. Eosinopenia, Lympocytopenia and Polycythemia are seen.
13. Increased excretion of 17 - Ketosteroids ( 17- oxosteroids) and 17 -
Hydroxycorticosteroids is seen.
IHYPERALDOSTERONISM I
1. Hyperaldosteronism may be primary or secondary. An excessive
production of aldosterone is commonly due to a tumour of the zona
glomerulosa.
2. This condition is termed as conn:S- disease or primary aldosteronism.
3. In this condition, Hypertension, Muscle weakness, Retention of
sodium, alkalosis etc is seen.
4. There is no oedema. Prolonged potassium depletion causes the
kidneys to result in polyuria. ·
5• The potassium depletion causes muscle weakness, metabolic alkalosis
which may lower the ionized calcium level resulting in tetany.

E,u:tocrir, S
e ysrem 363
6
' Sifecl~ndary hyperaldosteronism occurs in congestive heart failure, cirrhosis
0 IVe 't}
r WI 1 ascites, etc.
[ADRENOGENITAL SYNDROME I
1
· Adrenogenital syndrome will occur due to over production of adrenal
androgens.
2· This condition is associated with tumours of the adrenal cortex.
Clinical features: In feotal life:
1. Produces pseudo-hermaphrodites (eunuchs). Both male and female
characters are present in the same subject but incomplete.
In childhood:
1. In females, precocious sex development is seen. That is early
menstruation and breast formation.
2. In males, precocious growth of sex and body takes place.
In adults:
1. Reversal of sex characters is the main feature in adults.
2. In females, virilism occurs. The female changes into male. The face,
body appearance, voice becomes male type.
3. In females, beard, mustaches grow and menstruation stops. Uterus,
ovaries degenerates and clitoris enlarges.
4. In males, feminisation may occur but not common.
IPineal bodyI
1. The endocrine gland attached to the roof of the 3rd
ventricle is known
as pinealgland or epiphysis cerehri.
2. The gland is about 10mm long, reddish in colour. It is covered by a
capsule formed by the pia-mater and consists of masses of neuroglia
and secretory cells called pinealorytes.
3. The gland tends to atrophy after puberty and may become calcified
in later life.
4. Melatonin is the hormone sefc
1
rethed by the pthineal gland. Secretion
is influenced by the amount o ig t entering e eye.
5
. The secretion is highest at night and lowest in the midday.
6
. Although its functions are not fully understood, it is believed to be
associated with
i) Coordination ofthe circadian and diurnal rhythms ofmany tissues

Anatomy & Physiology for Para-Medics
364
ossibly by influencing the hypothalamus.
)
pnhib' • f wth and development of the sex organs before
ii I 1tion o gro .
b b bly by P
reventing synthesis or release of
pu erty pro a
g·onadotrophins.
[Pancreas I
l. Pancreas is the pale gray-colored leaf-like gland
1
s
1
ituated more or
less transversely over the posterior abdomin~ wa •. .
2. It is present in epigastric and left hypochondnac regions measunng
about 15cm length.
3. Pancreas is both an exocrine and endocrine gland.
IStructure I
1. Pancreas is divided into three parts.
1. Head
2. Body
3. Tail
2. Head lies in the "C" shaped curve of duodenum, body lies behind
the stomach, and tail lies in front of the left kidney and just reaches
the spleen.
3. Pancreas is made up of two types of cells.
1. Acini cells
2. Islets oflangerhans
4. Acini cells occupy 990/o of the gland. They are responsible for the
production ofmixture offluid and digestive enzymes called pancreatic
juice.
5. Islets of langerhans occupies only 10/o of the gland. These are
responsible for the production of hormones.
6. The islets of langerhans consist of four types of cells.
They are:
i) Alpha cells
ii) Beta cells
iii) Delta cells
iv) F- cells
7. The alpha cells secrete the hormone called glucagon which raises
the blood sugar levels.
8• The beta cells secrete the hormone called insulin which lowers
the blood sugar levels. ·
9. The delta cells secrete (GHIH) growth hormone inhibiting
hormone which inhibits the secretion of insulin and glucagon.
10. TheF - cells secretpancreatic polypeptide which regulates release
of pancreatic digestive enzymes.

Endocrin.e System 36.5
IAlpha cells )
I . Alpha cells secrete a hormone called glucagon.
2. The level of blood glucose directly controls glucagon secretion. The
fall in levels of blood glucose stimulates secretion of glucagon.
3: The hormone GHIH inhibits the secretion of gJucagon.
4. An increased activity of sympathetic division enhances the releasing
of glucagon.
IAction of glucagon J
1. The physiological activity ofglucagon is to increase the blood glucose
levels when it falls below normal.
2. Glucagon accelerates {glycogenolysis) the conversion ofglycogen into
glucose.
3. Glucagon promotes gluconeogenesis. lt is the formation of glucose from
lactic acid and certain amino ;u:ids.
4. Glucagon enhances the release of glucose into the blood as a result
of which blood glucose levels increases.
(Beta cells I
l. Beta cell secretes a hormone called insulin.
2. The blood glucose levels regulate the secretion of insulin.
3. Increased blood glucose levels encourage the secretion of insulin,
where as decreased blood glucose levels inhibit secretion of insulin.
4. The hormones GH and ACTH raise the blood g.lucose levels. This
will trigger the insulin secretion. The GHIH inhibits the secretion of
insulin.
5. Increased activity of parasympathetic division stimulates insulin
release.
IAction of insulin I
l. Its chief physiological function is opposite to that of glucagon. It
helps to adjust blood glucose level by decreasing the level ifnecessary.
2. Insulin accelerates the transport of glucose from the blood into the
cells, especially skeletal fibers.
3. Insulin accelerates glycogenesis that is the conversion of glucose into
glycogen.
4. lnsulin accelerates entry of amino-acids into the cells and synthesis
of proteins.
5. Insulin accelerates lipogenesisthatis the conversion ofglucose or other
nutrients into fatty acids.
6. Insulin decreases glycogenolysis.
7. It also decreases gluconeogenesis.

368
Anatomy & Physiology for Para-Medics
4. Each lobe consists of a deeply stained peripheral cortex and central
light stained medulla. . .
5. The medulla consists mostly of ep1thebal cells and more widely
scattered lymphocytes.
6. The epithelial cells produce thymic hormones, which are thought to
aid in maturation of T cells.
7. The hormones produced by the thymus gland are
1. Thymosin,
2. Thymic humoral factor (THF)
3. Thymic factor (TF)
4. Thymopoietin
10vanesJ
Ovaries are the female gonads that produce ovum and the following
hormones.
1. Estrogen
2. Progesterone
3. Relaxin
4. Inhibin
[These hormones are explained in detail under reproductive .rystem].
I1estesI
Testes are the male gonads that produce sperms and the foilowing
hormones.
1. Testosterone
2. lnhibin
[These hormones are explained in detail under reproductive .rystem].