2 thyroid booklet

Embryology of Thyroid Gland
Origin : Endoderm of floor of pharynx opposite the 1st pouch.
Development :
1. Endoderm of floor of pharynx ---> Thyroid bud ---> flask shaped --->
Crescent ---> solid bilobed
2. Ultimobranchial body prevent extra descend ---> gives parafollicular cells
3. Endodermal cells ---> follicular cells
4. Proximal part of bud ---> narrow ---> thyroglossal duct (stalk attached to
tongue) ---> degenerate ---> leaving foramen caecum in tongue.
5. In 50 % part of duct persists giving a pyramidal lobe attached to isthmus
Congenital Anomalies :
1. Agenesis ---> cretinism
2. Ectopic :-
a. Incomplete descend >> Sublingual & lingual thyroid
b. Extra descend >> Retrosternal Thyroid
3. Superficial Thyroid : Superficial to infrahyoid muscles
4. Persistent Thyroglossal Tongue
a. Remnants of duct gives accessory thyroid tissue
b. Thyroglossal cyst > Ruptures > gives Thyroglossal Fistula (skin)

Thyroid Gland
Largest endocrine organ in the body which weighs 25 grams
Site:-
In the front & sides of the lower part of the neck clasping the trachea
extending from C5 to T1
Shape:
Butterfly... Has two lobes right and left ones connected by the isthmus
It has:-
 Two lateral lobes
o Conical in shape
o Sup pale diverging upwards and laterally
o Lower lobe diverging downwards and laterally
 Isthmus
 Small pyramidal lobe
o may be present
o project upwards from the isthmus
o may be connected by fibroumuscular band called levator glandulae
thyroideae (remnants of thyroglossal duct in the embryo)
Extensions:-
 Apex : rests on the thyroid cartilage reaching it's oblique line

 Base : reach the level of 5, 6 tracheal rings
 Isthmus: crosses opposite the 2, 3, 4 tracheal rings
Relations :-
 Isthmus :-
Anterior relations :-
1- Skin & superficial fascia.
2- Ant jugular veins.
3- Deep fascia.
4- Sternohyoid & sternothyroid
Posterior relations :-
1. Trachea (2-3-4)
2. Upper border of isthmus > related to an anastomotic artery
3. Lower border of isthmus > gives rise of the right & left inferior
thyroid veins.
4. The pyramidal lobe may project upwards from the isthmus.
 Lateral lobes
 anterolateral surface (superficial surface):

1. skin , superficial fascia (containing platysma muscle) & deep
fascia
2. Its upper part is crossed by superior belly of omohyoid
3. Its middle part is covered by sternohyoid (superficially) &
sternothyroid (deeply)
4. Its lower part is overlapped by the anterior border of
sternomastoid
 Medial surface:
1. Upper part
a) Larynx: thyroid, cricoid cartilages & cricothyroid
muscle
b) Pharynx: inferior constrictor muscle
c ) External laryngeal nerve
2. Lower part
a) Trachea
b) cervical Oesphagus
c) External laryngeal nerve (in between)
 Posterior surface
a. inferior thyroid artery (before enter the gland)
b. common carotid arteries ( before inside the sheath)
c. longus coli muscle
d. parathyroid glands are embedded in the posterior surface.

Arterial supply :-
1- superior thyroid artery ( branch of ECA)
2- inferior thyroid artery (From thyrocervical trunk which is a branch of 1st
part SC)
3- Thyroidea ima arteries (Which arises from the arch of aorta ,
braciocephalic artery , or left common carotid artery) supply isthmus.
Venous drainage :-
3 pairs :-
1- The superior thyroid vein: ascends along the superior thyroid artery at
the apex of the lobe and becomes a tributary of the internal jugular
vein.
2- The middle thyroid vein: very short vein which arises from the middle
of the lobe and ends in the internal jugular vein.

3- The inferior thyroid veins: arises from the lower border of the isthmus
and adjacent part of the lobes. They descend anterior to the trachea
and collect into one vein which usually ends in the inominate vein.
Nerve supply (mainly ANS) :-
1- Parasympathetic fibers come from the vagus nerves.
2- Sympathetic fibers are distributed from the superior, middle, and inferior
cervical ganglia of the sympathetic trunk. These small nerves enter the
gland along with the arteries.
Applied anatomy :-
1) High ligation of the superior thyroid artery during thyroidectomy may cause
injury of the external laryngeal nerve, because superior to the upper pole of
the thyroid, the external laryngeal nerve runs with the superior thyroid
artery before turning medially to supply the cricothyroid muscle and in 21%
the nerve is intimately associated with the superior thyroid vessels.
2) Ligature of the inferior thyroid artery near the lower pole of the thyroid
gland can lead to injury of the recurrent laryngeal nerve as they are near.

Histology of the thyroid gland
Stroma
 It is covered by a double capsule
 Outer is derived from the cervical deep fascia, inner is the true C.T. capsule
of the gland.
 Sends fibrous septa penetrating the gland. Reticular fibers extend from the
septa and form a network surrounding the thyroid tissue.
 Carries the blood supply of the gland and gives support to the parenchyma.
Parenchyma
 The thyroid tissue is composed of follicles, round to oval, of different sizes
lined by cuboidal cells contain a gelatinous acidophilic material in their lumen
called colloid.
 The follicles are lined by two types of cells:
Follicular cells and parafollicular cells
Follicular cells Parafollicular cells
LM They are cuboidal cells with
central rounded nuclei and
basophilic cytoplasm resting on a
basement membrane.
ActiveColumnar
Inactive  Squamous
They are large cells with pale
cytoplasm and so are called
clear cells.
EM  The cell shows the
ultrastructural features of cells
secreting polypeptides :
(mitochondria, rough endoplasmic
reticulum, Golgi and secretory
vesicles).
 Golgi complex in these cells is
supranuclear and their small
secretory granules are apical
towards the lumen.
 Abundant apical phagosomes and
lysosomes.
 The cell membrane of the
luminal border has a moderate
number of microvilli.
 The cell contains the
organelles of polypeptides
secreting cells
(mitochondria, rER, Golgi
and secretory granules).
 The Golgi complex is
infranuclear and their
secretory granules are
small, dense and basal
towards the capillary bed.

Function Secretion of thyroid hormones
(T3 and T4).
Secretion of calcitonin which
lowers the blood calcium level
by inhibiting bone resorption.
Secretion of calcitonin is
stimulated by an elevation in
blood calcium concentration.
Steps of synthesis and secretion of T3 and T4
 The follicular cells synthesize thyroglobulin by the rER
 The Golgi A. adds carbohydrate intracellularly to the thyroglobulin.
 Secretory vesicles carry the thyroglobulin into the lumen of the follicle by
exocytosis where it contributes in the formation of the colloid.
 Trap the iodide from the capillary bed around the follicles and liberate it as iodine
in the follicular lumen where iodination of thyroglobulin takes place extracellularly
in the colloid.
 The colloid is phagocytosed by the follicular cells (phagosomes).
 Lysosomes fuse with the phagosomes, thus the reabsorbed thyroglobulin is
hydrolysed to T3 and T4 (thyroxine) which is released into the fenestrated blood
capillaries surrounding the follicles.
Hints:
 Clear cells or C cells:
o They form about 0.1% of the total number of cells.
o These cells are found as part of the follicular epithelium scattered
between the follicular cells.
o Their basal surfaces rest on basement membrane but their apical
surfaces never reach the lumen of the follicles.
o Parafollicular cells can also form isolated clusters between the
follicles.
 The Interfollicular cells are tangentially cut follicles so appearing as clumps
of cells without lumen. They may be follicular or parafollicular cells.
 Thyroid gland is the only endocrine gland which store big quantities of
hormones in an inactive form extracellularly in the follicular lumen.

 The thyroid gland secrete many important hormones such as T3 (tri-
iodothyronine), T4 (Thyroxin) and calcitonin.
 They exert a massive effect on multiple organs and systems such as:
a) Metabolic effects:
 It increases the BMR, energy utilization and heat production.
 It’s anabolic to protein metabolism in small doses and catabolic in larger
doses.
 It helps CHO absorption from GIT and enhances gluconeogenesis.
b) Effect on CVS:
 It increases sensitivity of cardiac B receptors to circulating catecholamines.
 It increases energy utilization.
 SBP is raised due to increased cardiac contraction and rate while DBP is
lowered due to VD caused by excessive heat production and CO2 release by
metabolic reactions.
c) Effect on growth:
 It stimulates growth due to its anabolic effect on protein metabolism.
 It helps GH activity.
d) Effect on mental development:
 It helps normal mental development during the first years of life and
stimulates normal myelination.
 It activates the RAS leading to hyperexcitability.
e) Effect on respiration:
Respiratory rate is increased due to heat and CO2 production.
It increases DPG in RBCs.
Regulation:
1) Hypothalamus:
Stimulatory: TRH
Inhibitory: Somatostatin

2) Pituitary gland: TSH
3) Negative feedback mechanism.
4) Blood iodine level.
5) Emotions.
6) Temperature.
Effects of TSH on the thyroid gland:
1) Helps iodide uptake by the gland.
2) Increases synthesis of hormones.
3) Increases hormone storage and release.
4) Increases size of the gland and cells.
5) Increases gland vascularity.
Pathology of Thyroid Gland
Hypothyroidism:
 Is a state of decreased level of T3 and T4 leading to hypofunctioning of the
body organs in response to hyposecretion of thyroid hormones.
Causes:
1. Agenesis, removal or destruction of the thyroid gland.
2. Interference with the synthesis of thyroid hormone.
3. Pituitary and hypothalamic disease.
4. Anti-thyroid activity of goiterin found in cabbage and turnip.
5. Idiopathic non toxic colloidal goiter.
It can be found in one of two forms according to the age of incidence.
 Hypothyroidism in adults is called Myxedema.
 Hypothyroidism in children is called Cretinism.

Myxedema:
Manifestations:
1. On nervous system:Mental functions are disrupted causing slow reflexes &
Thinking, poor memory and apathy.
 2. On CVS: All cardiac properties are decreased, Arteriosclerosis due to
cholesterol accumulation caused by increased fat anabolism. , Anemia &
carotenemia.
3. On Respiratory system: Hypoventilation.
4. On GIT: constipation, decrease metabolic rate.
5. Skin cold and dry.
6. Voice slow and husky.
Cretinism:
Causes:
Extreme hypothyroidism during fetal life, infancy and childhood
Manifestations:
 Growth retardation, mental retardation due to incomplete nerve myelination.
 Disproportionate growth and abdominal organs bulge in comparison to the
small, short stature of the cretin child.
 Enlarged tongue resembling mental retardation.
 Sluggish Movement

Thyrotoxicosis: or Hyperthyroidism:
Is a state of increased level of T3 and T4 in the circulation leading to
exaggeration in the normal effects of thyroid hormones and disturbing normal
body functions.
The commonest form of hyperthyroidism is Grave’s disease.
Manifestations:
 Enlarged gland, excessive sweating and heat intolerance, weight loss,
increased appetite, diarrhea, muscle wasting and exophthalmos.
 Tachycardia, tachypnea may also be found and may lead to arrhythmias and
sometimes heart failure.
 Skin is thickened due to over accumulation of proteins so it’s coarse.
Grave's disease:
Manifestations:
1. Thyrotoxicosis
2. Infiltrative ophthalmopathy
3. Infiltrative dermopathy.
Causes:
LATS bind to cell membrane receptor instead of TSH leading to continual
stimulation of these receptor and activation of C.Amp system with excessive
formation of thyroid hormone.
High levels of thyroid hormone suppress Ant. Pit. Formation of TSH
Pathogenesis:
1. Defect in suppressor T-cell
2. Proliferation of CD4+ T-helper cells
3. CD4+ cells work with B cells to produce Ab against TSH receptor
proteins.

Anti-TSH receptor Ab:
1. Thyroid stimulating Ab:
((Not in book just to understand properly)): Acts as LATS activates the cells in
longer and slower way than normal TSH leading to increase thyroid hormone.
2. Thyrotropin binding inhibitor Ab:
((Not in book just to understand properly)): inhibit normal union of TSH with its
receptor.
3. Thyroid growth stimulating Ab:
Proliferation of follicles and growth of thyroid gland.
Morphology of Grave's disease:
Gross Microscopic
Diffusely and symmetrically
enlarged.
Colloid pale scanty with scalloped
margins.
Soft and smooth. Follicles are closely packed.
Parenchyma on cut section has soft
meaty appearance.
Follicles in untreated cases are tall,
columnar and overcrowding.
Capsule intact not adherent. Overcrowding may lead to
intraluminal papillary formation
with no fibro vascular core.
Highly vascular. Highly vascular.
Lymphoid aggregates found in
interstitial tissue.
Manifestations of Hyperthyroidism:
1. In Graves ' disease the thyroid gland is enlarged with increase number of
cells and each cell increase its secretion.
2. Increase the metabolic rate 60-100%.
3. Intolerance to heat.

4. Increase sweating.
5. Muscle weakness.
Thyroditis
1. Infectious thyroditis:
a. Cause:
Infection by strep. , staph. aureus , Mycoplasma or fungi
b. Clinical picture:
painful enlargement of the gland
2. Riedel’s fibrosing thyroditis:
a. Cause:
Autoimmune fibrosing of unknown etiology >> replacement of the
thyroid tissue by fibrous tissue
 Atrophy of the gland & hypothyroidism
 Mistaken for infiltrating neoplasm
3. Hashimoto’s thyroiditis:
a. Cause:
Autoimmune inflammation of the thyroid
b. Morphology (2 forms):
Goitrous form Atrophic form
1. Grossly:
Diffuse symmetrical enlargement ( goiter) , firm & pale
2. Microscopically:
 Inflammation >> lymphocytes , plasma cells &
macrophage ifiltration ( small basophilic cells by L.M)
 Germinal centers
 Thyroid follicles:
a. Small
b. Lined by hurthle cells ot oncocytes ( eosinphilic )
 Delicate fibrosis
Small atrophic gland
with extensive
fibrosis

c. Clinical picture:
 Painless enlargement with hypothyroidism ( sometimes transient
hyperthyroidism in early cases)
 Small atrophic gland in late cases
 Prognosis is excellent
 Increased risk of B cell lymphoma
4. Subacute granulomatous thyroiditis:
a. Cause:
May be viral infection
b. Morphology:
Unilateral or bilateral enlargement, firm & intact capsule
I. Signs of infection:
 Fever
 Malaise
 Leukocytosis
 Increased ESR
 Painful enlargement >> hyperthyroidism
5. Subacute lymphocytic thyroiditis:
a. Cause:
Unknown etiology
b. Morphology:
Lymphoid infiltration but no germinal centers
 Enlargement of the thyroid >> hyperthyroidism
 Self limited may be followed by hypothyroidism

Thyroid tumors
In general almost all thyroid tumors arise from follicular cells except
medullary carcinoma from parafollicular cells
1. bengin neoplasms ( adenoma ):
a. Morphology:
 Solitary
 Well circumscribed
 Encapsulated , demarcated from surrounding tissues
 C.S:
 Compression of the surrounding tissue
 Gray-white to red-brown in color
 Areas of hemorrhage, fibrosis & calcification
 Pressure symptoms ( dysphagia , dyspenia )
 Hemorrhage >> rapid painful enlargement
 Mainly non functioning ( functioning >> hyperthyroidism )
2. Malignant neoplasms :
 Mainly carcinomas
 Sarcomas & lymphomas are rare
 More common in females in the puperty age with female:male ratio 3:1 or
2:1
 Hashimoto’s thyroiditis >> B cell lymphoma
 Genetic factors>> papillary & medullary carcinomas

Papillary carcinoma Follicular carcinoma
1. Most common ( 75:85% )
2. Earlier age ( 30:50 years)
3. Female : male ( 3:1 )
4. Grossly:
Solitary or multifocal
May be well circumscribed or
encapsulated
Sometimes ill defined margins and
infiltrating the surrounding tissue
5. Cut surface:
Granular
Fibrosis & calcification
Visible papillary processes
6. Microscopically :
Papillary structure ( fibrovascular stalk
cover by cuboidal epithelium
Ground glass nuclei
Psammomas bodies ( calcification)
7. Spread:
By lymphatics to head & neck lymph
nodes
Less common by the blood
8. Prognosis:
Excellent in 90% of female cases less
than 20 years old + localized tumor in
the gland & well differentiated
1. Less common ( 10:20% )
2. Older age ( 50 :60 years)
3. Female :male ( 3:1 )
4. Grossly:
May be well circumscribed or
encapsulated
Sometimes ill defined margins and
infiltrating the surrounding tissue
5. Microscopically:
Uniform cells forming small follicles
stimulating normal follicles
Tumor cells granular eosinophilic similar
to hurthle cells
( differentiated from hashimoto’s
thyroiditis by capsular & vascular
invasion of the tumor)
6. Spread:
Hematogenous to bones, brain, lungs
and liver
7. Prognosis:
Small encapsulated >> good prognosis
Large invasive >> bad prognosis , death
occurs within 10 years

Medullary carcinoma with
multiple endocrine syndrome ( familial )
Medullary carcinoma (sporadic cases)
1. Arise from C cells secreting calcitonini &
other peptide hormones as serotonin,
somatostatins & vasoactive intestinal
peptides
2. Less common 20% of medullary carcinoma
3. Occurs at younger age ( 30:40 years )
4. Pathogenesis : Genetic factors
5. Grossly:
Bilateral & multicentric
6. Microscopically:
Polygonal to spindle shaped cells in
nests . trabeculae or follicules
Amyloid stroma in 50% of cases
7. Clinical picture:
Present with manifestations of peptide
hormone secretion ( diarrhea due to
calcitonin or vasoactive peptide )
8. Prognosis:
Better ( 10 year survival rate is 70% )
1. Arise from C cells
2. More common 80% of medullary carcinoma
3. Occurs at older age ( 50:60 years )
4. Grossly:
Discrete tumors in one lobe
5. Microscopically:
Polygonal to spindle shaped cells in
nests . trabeculae or follicules
Amyloid stroma in 50% of cases
6. Clinical picture:
Thyroid mass with dysphagia ,
hoarseness of voice or cough
7. Prognosis:
Worse ( 10 year survival rate is 40% )
5. Anaplastic carcinoma:
Most aggressive human neoplasm
Occurs in elderly people in areas of endemic goiter
Grossly:
 Bulky mass grows extensively beyond the capsule to the
surroundings
Microscopically:
 Highly anaplastic cells, large or small, multinucleated
Prognosis: very bad ( death occurs in less than one week )

Drugs used to treat Hypothyroidism:
Pharmacodynamics :
T4 and T3 dissociate from TBG ,, entering cell by diffusion or active transport ,,
T4 is converted to T3 ,, T3 enters nucleus ,, binding to specific receptor ,,
activating m-RNA and protein synthesis ,, so this takes long time
Pharmacokinetics :
 Half life of T4 is 7 days but that of T3 is 2 days ,,
 Deactivated in liver by de-conjugation and excreted as glucuronide and
sulphate in liver and partly in urine
Thyroid Preparations:
1. L-Thyroxin
2. L-Thyroxin sodium : IV for Myxodema coma
3. Liothyronine sodium : more potent , faster in action , shorter duration ,
rapid absorption from GIT
4. Liotrix : mixture of levothyroxin and Liothyronine in ratio 4:1
Therapeutic uses:
Replacement therapy in : Hypothyroidism, Cretinism, Myxodema Coma
,(Hydrocortisone may be needed as prolonged hypothyroidism is associated with
adrenal or pituitary insufficiency
Adverse effects:
 Tremors ,, Nervousness ,, Insomnia
 Weight loss ,, Heat intolerance
 Tachycardia, Arrhythmia, Anginal pain ( liable to be provoked by vigorous
therapy so thyroxin must be stopped for a week and began again at lower
doses )
Drug Interactions :
Antacids containing Ca and Al decrease T4 absorption but not T3 ,, enzyme
inducers as phenobarbital enhance their metabolism

Preparations Used In Hyperthyroidism :
Iodides Thiourea derivatives Radioiodine
Pharmacokinetics : Given orally ,, but
shouldn't last for
more than 2 weeks ,,
as condition will be
worse
Propyl thiouracil: rapidly
absorbed, excreted by kidney
as inactive glucuronides, half
life is 1,5 hrs , poorly crosses
placental barrier so can be
used with pregnant women
inhibits coversion of T4 to T3
Carbimazole prodrug its active
form is methimazole
Thioamides are metabolized in
liver, excreted in urine as
sulphate esters and
glucronides
Rapidly absorbed
from GIT , cytotoxic
effects delayed for
1-2 months , maximal
effect after 3-4
months
Mechanism of
action
not clear but has
effect opposite to
TSH , as decreasing
I trapping, thyroid
hormone synthesis
and release, size and
vascularity of thyroid
gland
Reduce thyroid hormone
formation by inhibition of
thyroid peroxidase to block I2
organification (formation of
iodotyrosine ) , inhibiting
coupling of iodotyrosines to
form T3 and T4
Onset of action is 2-3 weeks
Beta radiation
emission having
destructive effect on
thyroid cells , and
gamma rays useful
for estimating
quantity of
radioactive material
in gland by Geiger
counter
Therapeutic
uses
Preparation of
thyrotoxic patients
for surgery
(thyroidectomy ) :
given 7-10 days
before operation to
reduce vascularity of
gland
Thyroid crisis : rapid
onset to inhibit
hormone release
Preparation of patients for
surgery
Chronis treatment of
hyperthyroidism
Management of thyrotoxicosis
Treatment of some
cases of
hyperthyroidism
In combination with
surgery in cases of
thyroid carcinoma
Diagnosis of thyroid
gland function by
measuring 24 hrs I132
uptake
Adverse effects  Metallic taste,
diarrhea,
 Sore mouth and
Papular skin rash
Lymphoadenopathy
Leucopoenia, agranulocytosis,
Hypothyroidism

throat, excessive
salivation with
painful salivary
glands
 Coryza like
syndrome,
productive cough
 Skin rash, drug
fever
aplastic anaemia so blood
count should be done in case
of infection or anaemia
Thyroid enlargement with
increased vascularity
Contraindications Pregnancy except propyl
thiouracil
Lactation as it is concentrated
in milk
In children and
pregnancy
Drugs Controlling Peripheral effects of Hyperthyroidism :
Beta receptor blockers as propranol (20-40 mg orally every 6 hrs ) if
contraindicated , Diltiazem (90-120mg) 3 or 4 times daily used
Thyroid Crisis:
Libration of large amount of thyroid hormones in blood, life threatening treated
by :
 Propranol if contraindicated give diltiazem
 Potassium iodide
 Thiouria
 Mental disturbance treated by with chloropromazine
 Hyperpyrexia treated with cooling or aspirin
 Hydrocortisone

Essay Questions
1. Give the origin of the tongue
2. Give the origin of each of the following:
a. thyroid bud
b. thyoid follicles
c. parafollicular cells
d. pyramidal lobe & levator glandulae thyroidae
3. Give short account on develpoment of thyroid gland
4. Mention the congenital anomalies of thyroid gland. Discuss two of them.
5. From which pharyngeal arches arise each of the following:
a. thyroid bud
b. parafollicular cells
6. What is the surface anatomy of the thyroid gland?
7. What are the relations of the isthmus of the thyroid gland ?
8. What are the relations of the lateral lobes of the thyroid gland?
9. What is the arterial supply of the thyroid gland and there origin?
10. What is the venous drainage of the thyroid gland/?
11. What is the nerve supply of the thyroid gland?
12. Discuss the applied anatomy on thyroectomy?
13. Compare between follicular and parafollicular in the parenchyma of the
thyroid gland
14. Correlate the EM structure of follicular cells to its function
15. From the diagram
 Mention the names of these
processes A,B
 Mention the names of the
organelles 1,2 and 3
 Mention the hormones (4)
secreted by this cell

16. Discuss the metabolic functions of Thyroid hormones on metabolic rate
and protein synthesis.
17. Discuss the metabolic functions of Thyroid hormones on fat and
carbohydrate metabolism.
18. Explain the functions of Thyroid hormones on growth and development.
19. Explain the functions of Thyroid hormones on cardiovascular system.
20.Discuss the effect of thyroid hormones on respiration and GIT.
21. Enumerate 4 regulatory mechanisms on thyroid hormones secretion
22.Explain the hypothalamic and pituitary regulation on Thyroid hormones
secretion.
23.What’s meant by Hypothyroidism?
24.Mention 3 of the causes of Hypothyroidism
25.Discuss how can some food cause Hypothyroidism, and give an example
26.Mention 3 factors that interfere with thyroid hormone synthesis.
27.Demonstrate the pathogenesis of Idiopathic non-colloidal goiter.
28.Classify the diseases caused by Hypothyroidism in
 Adults
 Children
And mention 3 manifestations to each.
29.Mention the effect of myxedema on each of the following:
 Metabolic rate
 Skin
 Voice
 Muscles
 CVS
 GIT
 Respiration
 Nervous system
 Bone marrow
 Vessels
30.What’s the cause of each of the following with myxedema:
 Yellow skin
 Dry skin
 Hypoventilation
 Anemia
 Constipations

 Patient have poor memory
 Anemia
31. Give short account on myxedema edematous swellings.
32. Define the cretinism.
33.What are the common causes of cretinism?
34.Mention 3 of the manifestations of cretinism
35.Demonstrate the manifestation of cretinism in:
 Newborn baby
 Few weeks after birth
36.Why the Newborn babies affected with cretinism have normal
appearance?
37.What are the manifestations of mental retardation in infants with
cretinism?
38.What are the manifestations of physical retardation in infants with
cretinism?
39.What happen in case of the therapy not begin soon after birth in case of
child with cretinism?
40.How can hypothyroidism be diagnosed?
41. In which case of hypothyroidism occur each of the following:
 Decrease Thyroid hormone level
 Increase TSH serum level
 Abnormality in T hormone but TSH levels not increased
42.Mention the most common cause of hyperthyroidism, and mention its
causes.
43.Demonstrate the triad of manifestation of Graves’ disease.
44.What’s the incidence peak of Graves’ disease, mention the ratio males:
females?
45.What are the causes of Graves’ disease?
46.Give short account on the pathogenesis of Graves’ disease.
47.Explain... Graves’ disease is an autoimmune disease.
48.Mention 3 of anti-TSH-receptors Abs , and their actions
49.Demonstrate the morphology of each of the following in case of Graves’
disease:
 Thyroid gland
 Lymphoid tissues
 Heart

 Orbital muscles
 Eyes
50.Mention 6 of manifestations of Graves’ disease, discuss 3 of them.
51. What’s the cause of each of the following in case of Graves’ disease:
 Enlarged thyroid gland
 Tolerance to heat
 Soft wet skin
 Inability to sleep
 Tremors of stretched fingers
 Weight loss
 Diarrhea
 Exophthalmoses
 Muscle weakness
52.Mention the laboratory diagnosis of Graves’ disease.
53.What arethe types of colliod goiter?
54.Compare between hyperplastic stage and colloid involution stage of simple
diffuse goiter?
55.What are the conditions interfe with thyroid hormone synthesis?
56.Enumerate types of thyroiditis
57.Define Hashimoto’s thyroiditis and its variants, and then discuss its
prognosis.
58.Describe the morphology of Hashimoto’s thyroiditis.
59.Explain the clinical features of subacute granulomatous thyroiditis
60.Describe the morphology of adenomas. (gross & cut section)
61. Discuss the incidence & pathogenesis of thyroid carcinomas.
62.Compare between thyroid carcinomas according to: Morphology, Incidence
& Prognosis
63.Discuss the therapeutic uses of adrenocorticotrophic hormone ACTH
64.Enumerate the therapeutic uses of oxytocin
65.Enumerate the therapeutic uses of ADH(vasopressin)
66.Give a short account on preparation and administration of oxytocin
67.Explain the therapeutic uses of bromocriptine
68.Mention the therapeutic uses of growth hormone and thyroid stimulating
hormone TSH

69.Give a short account on desmopressin
70.Discuss the pharmacodynamics of thyroid hormones T3, t4 as a treatment
of hypothyroidism
71. Explain the time lag of hours or days for the hormone T3 , T4 to give
maximal response after administration.
72.Discuss the pharmacokinetics of thyroid hormones T3 , T4
73.Give a short account on Thyroid Preparations
74.Mention the therapeutic uses of the thyroid preparations and some its
side effects
75.Discuss the mechanism of action of iodides
76.Give a short account on pharmacokinetics of iodides
77.Mention the therapeutic uses of iodides
78.Enumerate the side effects of iodides
79.compare between thiourea derivatives (thioamide) and radioiodine in the
treatment of hyperthyroidism
80.list how to treat thyroid crisis (thyroid storm)

MCQs
1. All of the following is correct
about the development of
thyroid gland EXCEPT :
a. The thyroid bud develops
from the floor of the
pharynx opposite to the
first pouch
b. The ultimobrachial body
forms the parafollicular
cells which secretes
calcitonin
c. Thyroid gland is
ectodermal in origin
d. The thyroglossal tongue is
formed from the distal
part of the thyroid bud
e. A & C
f. C & D
2. What prevents the further
descend of the blind end of the
thyroid bud in the thorax :
a. Tuberculum impar
b. Ultimobranchial body
c. The copula of his
d. Hypobrachial eminence
e. None of the above
3. Endodermal cells of thyroid bud
forms the parafollicular cells
which secretes thyroxin
hormone
a. True
b. False
4. Persistant thyroid duct can lead
to all of the following EXCEPT:
a. Formation of thyroglossal
cyst
b. Formation of accesory
thyroid tissue
c. Formation of lingual and
sublingual thyroid
d. Non of the above
5. Retrosternal thyroid gland is
formed due to incomplete
descend of the thyroid bud
a. True
b. False
6. In 50% part of the thyroid
duct presists attached to the
isthmus which leads to
formation of :
a. Thyroglossal cyst
b. Accesory thyroid tissue
c. Thyroid fistula
d. Pyramidal lobe
e. None of the above
7. The weight of thyroid gland is :
a. 10 gm
b. 25 gm
c. 30 gm
d. 50 gm

8. The beginning of the thyroid
gland is at the level of :
a. C4
b. C5
c. C6
d. C7
9. The level of the end of the
base of lateral lobes of thyroid
gland is :
a. 1st
tracheal ring
b. 5th
cervical vertebra
c. 6th
tracheal ring
d. 5th
tracheal ring
10. Which of the following is
anterior to the isthmus ?
a. Anterior jugular veins
b. Trachea Rings 2,3,4
c. Anastomotic artery
d. Pharynx
11. All of the following is
related to the isthmus except :
a. Anterior jugular veins
b. Sternohyoid muscle
c. Sternomastoid muscle
d. Deep fascia
12. How many surfaces does
lateral lobe of thyroid gland
have?
a. 1
b. 2
c. 3
d. 4
13. All of the following is
related to superficial surface
of the lateral lobes except :
a. Superior belly of omohyoid
muscle
b. Posterior border of
sternomastoid muscle
c. Pretracheal fascia
d. Platysma muscle
14. Which of the following
nerves is related to the lower
part of the medial surface of
the lateral lobe of thyroid
gland ?
a. External laryngeal nerve
b. Recurrent laryngeal nerve
c. Vagus nerve
d. None of the above
15. Superior thyroid artery is
branched from :
a. Arch of Aorta
b. ECA
c. CCA
d. ICA
16. Thyrocervical trunk is
branched from :
a. 1st
part of subclavian
artery
b. 2nd
part of subclavian
artery
c. 3rd
part of subclavian
artery
d. Inominate artery

17. Superior thyroid vein is
related to which part of the
lobe:
a. Apex
b. Base
c. Posterior
d. Anterolateral
18. Ligature of the superior
thyroid artery may lead to
affecting :
a. External laryngeal nerve
b. Cricothyroid muscle
c. Low voice
d. All of the above
19. Inferior thyroid vein
collects in :
a. Innominate vein
b. SVC
c. External jugular vein
d. Internal jugular vein
statements is true??
a. Thoracic oesophegus is
related to the lower part
of medial surface of
lateral lobe of thyroid
gland
b. Longus coli is related to
the anterior of isthmus
c. Posterior to the isthmus
we have 2 tracheal rings
d. Pyramidal lobe projects
above the isthmus
21. When they are active,
follicular cells become:
a. squamous
b. columnar
c. pseudostratified
d. none of the above
22. The secretory vesicles of
follicular cells are:
a. apical
b. basal
c. central
23. Golgi complex of follicular
cells is :
a. supranuclear
b. infranuclear
c. central
24. Contain abundant
lysosomes:
a. oxyphil cell
b. follicular cell
c. parafollicular cell
d. all of the above
25. Iodination of thyroglobulin
takes place in :
a. the follicular lumen
b. follicular cells
c. a&b

26. Hydrolysis of thyroglobulin
to T3 & T4 takes place in :
a. colloid
b. follicular cells
c. a&b
27. Clear cells responsible for
synthesis of
a. thyroxin
b. parathormone
c. calcitonin
28. In clear cells , golgi
complex is :
a. supranuclear
b. infranuclear
c. central
True or False:
29. Follicular cells are cuboidal
cells with central nuclei and
acidophilic cytoplasm
30. Follicular cells when active
become squamous
31. Parafollicular cells cannot
reach the lumen of the follicles
32. Thyroxine injection
produces all of the following
effects except:
a.Increased pulse pressure and
water hammer pulse
b.Marked increase in both
oxygen consumption and
BMR
c.Decrease in plasma
cholesterol level
d.Decrease in rate of lipolysis
33. The thyroid hormones tend
to:
a.Increase the peripheral
resistence
b.Increase duration of tendon
reflex
c.Increase frequency of
defecation
d.Decrease the energy
expenditure required for a
certain work
e.Decrease pulse pressure and
heart rate
statements about The thyroid
hormones is incorrect:
a.They have a calorigenic
action
b.Increase rate of ATP
formation
c.Slows down utilization of
glucose
d.Their excess may cause
diarrhea
e.Have a lipogenic effect

35. Carotenemia may result
from
a.Deficiency of The thyroid
hormones
b.Excessive The thyroid
hormones
c.None of the above
statements about The thyroid
hormones is correct:
a.Have no role in lipid
synthesis
b.Promote brain growth in
adults
c.Increase systolic and
diastolic blood pressure
d.Their excess results in
continuous sleeping
e.Have a direct stimulating
action on the SA node
37. all of the following effects
of The thyroid hormones are
correct except:
a.increase rate of blood flow
to the skin
b.increase the no. of β
adrenergic receptors in the
heart
c.increase Haemoglobin
affinity to oxygen
d.increase milk secretion in
lactating women
38. The thyroid hormones
increase the heart rate by
which of the following
mechanisms
a.Direct stimulatory effect on
the SA node
b.Bainbridge reflex
c.Increase the sensitivity of
nodal cells to the
circulating catecholamines
d.All of the above
leads to an increase in the
thyroid hormones production:
a.Somatostatin
b.Decreased intake of iodine
c.Exposure to cold
d.Stress
e.C and d
40. All of the following are
effects of TSH on the thyroid
gland except:
a.Increase its vascularization
b.Decrease iodine
intracellularly in glandular
cells
c.Enhance proteolysis of
thyroglobulin
d.Increased secretions from
thyroid cells

causes of primary
thyrotoxicosis except:
a.Multinodular goiter
b.Tsh adenoma of pituitary
gland
c.Grave's disease
d.Toxic adenoma of thyroid
gland
42. The following are
hyperthyroidism non associated
causes of thyrotoxicosis:
a.Granulamatous thyroiditis
b.Struma ovari
c.Grave's disease
d.Exogenous thyroxine intake
43. Cardiac symptoms of
grave's disease include:
a.Bradychardia
b.Decreased cardiac output
c.Decreased pulse pressure
d.Palpitation
44. The cause of the tremors
in grave's disease is:
a.Increased activity of the
area controling muscle tone
b.Increased metabolic rate
c.Incrased RAS activity
45. Laboratory diagnosis of
thyrotoxicosis includes:
a.Elevated T3 and T4 level
b.Decreased TSH level
c.Elevated radioactive iodine
uptake
d.All of the above
causes of hypothyroidism
except:
a.Agenesis of the gland
b.Goitrins
c.Grave's disease
47. Skin changes in myxedema
include:
a.Soft
b.Yellowish color
c.Wet
d.Wrinkling
48. Manifestations of
hypothyroidism include all of
the following except:
a.Soft wet skin
b.Decreased metabolic rate
c.Husky vioce
d.Anaemia
49. Apathy is amanifestation
of:
a.Grave's disease
b.TSH adenoma in pituitary
gland
c.Granulomatous thyroiditis
d.Myxedema
50. Myxedema causes:
a.Constipation
b.Diarrhea
c.Vomiting
d.G.I.T upset

51. Delayed closure of the
fontaneles is amanifestation of:
a.Grave's disease
b.Myxedema
c.Cretinism
d.Struma ovarii
TRUE OR FALSE:
52. In cretin, skeletal and soft
tissue growth is inhibited.
53.TSH level is increased in
hypothyroidism due to
hypothalamus and pituitary
disorders.
54. All the following are cause
of primary hyper thyrodism
except :
a. Multinodular goiter
b. Adenoma of pituitary gland
c. Grave’s disease
d. Adenoma of thyroid gland
55. All the following are triad
of grave’s disease except:
a. Thyrotoxicosis
b. It’s an autoimmune disease
c. Infiltrative
ophthalmopathy
d. Infiltrative dermopathy
56. Which state is true about
grave’s disease:
a. It occur in old age
b. It occur due to defect in
DR gene
c. It’s due to defect in B-
cells
d. Cause generalized
hyperplasia of lymphoid
tissue
e. B & D
57. All the following are anti
TSH receptors ABs except:
a. TsAB
b. TBI-IG
c. TRH
d. TGIG
58. the most characteristic
feature of thyroid gland with
graves disease is
a. Extremely vascular
b. Capsule adherent
c. Small in size
d. Meaty appearance
59. The most clinical feature
for diagnosis of diffuse toxin
hyperplasia of thyroid gland :
a. Hyper trophy of lymphoid
tissue
b. Exophthalmos
c. Hyper atrophy of the
heart

60. what state is true about
colloid goiter:
a. May due to enzaymatic
defect
b. TSH increase in serum
while T3-T4 decrease
c. Secondary to iodine
deficiency
d. All the above
61. In the colloid involution
stage the follicle cells are:
a. Columnar
b. Cuboidal
c. Flattened
62. Which is true about multi
nodule goiter :
a. The first stage of goiter
b. It may end by hemorrhage
,scarring
c. Its non toxic
d. All the above
63. All are feature for nontoxic
multi nodule goiter except:
a. Oesophageal compression
b. Diarrhea
c. Trachea compression
d. Obstruction of inf.vena
cava
64. Multinodular goiter
different from graves in :
a. Occur in young age
b. Ophthalmopathy,
dermopathy not occurred
c. Toxicity is high
d. All the above
65. Adenomas incidence is
______ related to the age :
a. Directly
b. Indirectly
c. Not
d. Not specified relation
characteristics of adenomas
except :
a. Solitary
b. Infiltrative
c. Well demarcated
d. Spherical
more likely to occur in
adenomas ?
a. Hemorrhage
b. Hyperthyroidism
c. Malignant transformation
d. Remain in same size
68. The ratio of incidence of
thyroid carcinoma between
young male (below 18) and
young female below 18 is :
a. 2:1
b. 3:1
c. 1:1
d. (a) and (b)
more likely to occur in
carcinomas :
a. Papillary
b. Follicular
c. Medullary
d. Anaplastic

70. Papillary carcinoma is more
incident in which age :
a. 25 years
b. 45 years
c. 65 years
d. 70 years
true about papillae in papillary
carcinoma except
a. Psammoma bodies are
found
b. Fibrovascular core
c. Papilla like Greve's disease
d. Cuboidal cells are found
72. Which of the following have
Hurthe cells ?
a. Adenomas
b. Papillary carcinomas
c. Follicular carcinomas
d. Both (a) and (c)
secreted by medullary
carcinoma except :
a. Calcitonin
b. Thyroxin
c. Somatostatin
d. Serotonin
true about medullary carcinoma
in MEN syndrome except :
a. More incident in 3th to 4th
decade
b. Familial
c. Multicentric
d. Worse prognosis
related to the endemic goiter :
a. Anaplastic carcinomas
b. Follicular carcinomas
c. Papillary carcinomas
d. Both (a) and (c)
e. All of the above
76. Painful enlargement of
thyroid gland can occur in :
a. Multinodular colloid goiter
b. Infectious Thyroiditis
c. Thyroid adenoma
d. All of the above
true about subacute
granulomatous thyroiditis
except :
a. Self limited
b. More common in females
c. Capsule is disrupted
d. Hyperthyroidism occurs
78. Which of the following are
self limited :
a. Hashimoto thyroiditis
b. Granulomatous thyroiditis
c. Lymphocytic thyroiditis
d. Both (b) and (c)
79. Which of the following has
the risk of B-cell lymphoma ?
a. Hashimoto thyroiditis
b. Infectious thyroiditis
c. Subacate lymphocytic
thyroiditis
d. De Quervain's thyroiditis

80. The diagnostic agent useful
in identifying both hypo and
hyper thyroidism is:
a. thyroxine
b. tri-iodothyrosine
c. thyroid stimulating
hormone
d. thyrotropine – releasing
hormone
e. long acting thyroid
stimulators.
81. Indications of thyroid
hormones are following,
EXCEPT:
a. Cretinism
b. Myxoedema
c. Hashimoto's disease
d. For treatment of simple
obesity
82. All the following is true
regarding the thyroid hormones
EXCEPT:
a. Inactivation of thyroid
hormones occurs mainly in
the liver.
b. The half-life of T4 is 7
days whether that of T3 is
only 2 days.
c. T4 enters the nucleus then
binds to specific receptor
protein inside the nucleus.
d. There is time lag of hours
to days for thyroid
hormones to give maximum
response.
83. The preferred thyroid
preparation for maintenance
replacement therapy is:
a. liothyronine
b. iodides
c. levothyroxine
d. liotrix
84. Treatment of myxedema
coma can include all the
following drugs EXCEPT
a. hydrocortisone
b. levothyroxine
c. liothyronine sodium
d. carbimazole
85. The most physiological
preparation of thyroid hormones
is:
a. levothyroxine
b. liotrix
c. liothyronine sodium
d. L-thyroxin sodium
86. Side effects of thyroid
hormones replacement therapy
may include all the following
EXCEPT:
a. insomnia
b. weight loss
c. angina pain
d. exophthalmos

87. Iodides act by which of the
following mechanism:
a. by inhibiting thyroid
peroxidase & coupling
b. by decreasing I-trapping
and synthesis
c. by decreasing the release
of thyroid hormones.
d. b&c
e. a&c
88. Before thyroidectomy, the
lactating patient can receive :
a. iodides
b. carbimazole
c. L-thyroxin
d. thio-amides
89. Which of the following best
describes the effect of
propylthiouracil on thyroid
hormone production?
a. It blocks the release of
thyrotropin-releasing
hormone.
b. It inhibits uptake of iodide
by thyroid cells.
c. It prevents the release of
thyroid hormone from
thyroglobulin.
d. It blocks iodination and
coupling of tyrosines in
thyroglobulin to form
thyroid hormones.
e. It blocks the release of
hormones from the thyroid
gland.
90. Thyroid crisis should be
treated by:
a. propranolol
b. carbimazole
c. potassium iodide
d. hydrocortisone
e. all the above
91. Which of the following is a
safe drug for pregnancy can be
used for treatment of
thyrotoxicosis:
a. L-thyroxin
b. b carbamazole
c. propyl thiouracil
d. thioamides

Answers
1-F
2-B
3-B
4-C
5-B
6-D
7-B
8-B
9-D
10- A
11- C
12- C
13- B
14- D
15- B
16- A
17- A
18- D
19- A
20- D
21- b
22- a
23- a
24- b
25- a
26- b
27- c
28- b
29- False
30- False
31- True
32- D
33- C
34- C
35- A
36- E
37- C
38- D
39- C
40- B
41- B
42- C
43- D
44- A
45- D
46- C
47- B
48- A
49- D
50- A
51- C
52- False
53- False
54- b
55- b
56- e
57- c
58- d
59- b
60- d
61- c
62- b
63- b
64- b
65- A
66- B
67- A
68- C
69- A
70- B
71- C
72- D
73- B
74- D
75- D
76- D
77- C
78- D
79- A
80- C
81- D
82- C
83- C
84- D
85- B
86- D
87- D
88- A
89- D
90- E
91- C

2 thyroid booklet

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2 thyroid booklet