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37
Thyroid Gland
Surgical anatomy
Physiology
Thyroid function tests
Clinical examination
Goitre
Multinodular goitre
Retrosternal goitre
Toxic goitre
Graves’ disease
INTRODUCTION
Thyroid gland is an endocrinal gland present in the neck
secreting T
and T4 hormones. It is richly vascular and
3
highly functional. Effects of hormonal changes affect
every part of the body such as central nervous system,
cardiovascular system, gastrointestinal system and
reproductive system. It is also the site of various
diseases—a simple enlargement, toxicity and malignant
transformation.
Malignant tumours
Papillary carcinoma
Follicular carcinoma
Anaplastic carcinoma
Medullary carcinoma
Solitary nodule
Thyroiditis
Lingual thyroid
Ectopic thyroid
SU22.1: Describe the applied anatomy and physiology of
thyroid.
SURGICAL ANATOMY OF THYROID GLAND
Development and Anatomy
• It develops from median downgrowth (midline diver-
t
iculum) of a column of cells from the pharyngeal
floor between first and second pharyngeal pouches.
• The descent is anterior to structures that form hyoid
bone and larynx (Fig. 37.1).
• By 6 weeks of intrauterine life, the central column,
which becomes the thyroglossal duct, gets reabsorbed.
• The duct bifurcates to form thyroid lobes.
Tubercle of Zuckerkandl: It is a posterolateral
extension of thyroid gland. Incidence—30–40%. Arises
Fig. 37.1: Development of thyroid gland
from lateral anlage. It is closely related to recurrent
laryngeal nerve at surgery. Tubercle points to the
intersection between the nerve and inferior thyroid
artery. It should be removed, if present specially in
thyroidectomy for malignancies.
• Pyramidal lobe is formed by a portion of the
duct.
• Calcitonin producing parafollicular cells or C cells
originate from the fourth branchial pouch.
• Thyroid gland is present in the neck, enclosed by
pretracheal fascia which is a part of deep cervical
fascia. It has a right and left lobe joined by the
394
Thyroid Gland
395
isthmus in front of 2nd, 3rd and 4th tracheal rings.
It weighs about 20–25 g. A projection from the
isthmus usually on the left side is called pyramidal
lobe. It is attached to the hyoid bone by a fibrous
band or muscle fibres called levator glandulae
thyroideae.
• Thyroid is covered by true capsule which cannot
be separated. However, another layer (false capsule)
which is surrounding thyroid gland can be separated.
• Suspensory ligament of Berry: This pair of strong
condensed connective tissue binds the gland firmly
to each side of cricoid cartilage and upper tracheal
rings.
• Pretracheal fascia, which is part of deep cervical
fascia splits to invest the gland. These structures
(ligament of Berry and pretracheal fascia) are responsible for thyroid gland moving with deglutition.
Arterial Supply (Fig. 37.2)
• Superior thyroid artery, a branch of the external
carotid artery, enters the upper pole of the gland,
divides into anterior and posterior branches and
anastomoses with ascending branch of inferior
thyroid artery. Since the upper pole is narrow,
ligation is easy.
• Inferior thyroid artery is a branch of thyrocervical
1
and enters the posterior aspect of the gland.
trunk
It supplies the gland by dividing into 4 to 5 branches
which enter the gland at various levels (not truly
lower pole).
• Inferior thyroid artery used to be ligated well away
from the gland to avoid damage to RLN. However,
ligation of these arteries on both sides will cause
permanent hypoparathyroidism. Hence, the current
practice is to identify and ligate the branches of inferior
thyroid artery (3–4) separately.
• Thyroidea ima artery is a branch of either brachio-
cephalic trunk or direct branch of arch of aorta and
enters the lower part of the isthmus in about 2 to 3%
of the cases.
Venous Drainage
2
• Superior thyroid vein
drains the upper pole and
enters the internal jugular vein. The vein follows the
artery.
3
• Middle thyroid vein is single
, short and wide and
drains into internal jugular vein.
• Inferior thyroid veins form a plexus which drain into
innominate vein. They do not accompany the artery.
• Kocher’s vein is rarely found (vein in between
middle and inferior thyroid veins).
Fig. 37.2: Surgical anatomy of the thyroid gland. Arterial supply is shown on the right side and venous drainage is shown on the
left side
1
Branches of thyrocervical trunk can be remembered as SIT—suprascapular, inferior thyroid and transverse cervical artery.
2
Superior thyroid artery and vein are like newly married couple, they go together, hand-in-hand.
3
Middle thyroid vein is single, a bachelor and inferior thyroid artery and vein are a divorced couple.
Section II • General Surgery
396
Manipal Manual of Surgery
Nerves in Relationship with Thyroid Gland
1. Superior laryngeal nerve S(LN): The vagus nerve
gives rise to superior laryngeal nerve, which
separates from it at skull base and divides into two
branches. The larger internal laryngeal nerve is
sensory to the supraglottic larynx. The smaller
external laryngeal nerve runs close to the superior
thyroid vessels and supplies cricothyroid. This nerve
1
has been called as Amelita Galli-Curci nerve
.
• This nerve is away from the vessels near the upper
pole. Hence, during thyroidectomy, the upper
pedicle should be ligated as close to the thyroid as
possible.
• Cricothyroid space of Reeves: It lies between the
cricothyroid muscle medially and upper pole of
the thyroid lobe laterally. When we hold the upper
pole of the thyroid gland with Babcock’s forceps
and retract the lobe infero-laterally, it opens up
the space and SLN will be visible.
2. Recurrent laryngeal nerve (RLN) is a branch of
vagus, hooks around ligamentum arteriosum on the
left and subclavian artery on the right and runs in
the tracheoesophageal groove near the posteromedial
surface. Close to the gland, the nerve lies in between
(anterior or posterior) branches of inferior thyroid
artery (Figs 37.3 and 37.4 in the Riddle’s triangle).
• On the right side, it is 1 cm within the tracheo-
esophageal groove (Key Boxes 37.1A and B).
Key Box 37.1A
Recurrent Laryngeal Nerve at Surgery
Lack of colour—white in colour
Lack of elasticity
Lack of pulsation
Longitudinal vein on the surface
Longitudinal course
Location—Riddle’s triangle—it
is between inferior thyroid
artery superiorly, carotid artery
laterally and trachea medially.
From here RLN runs upwards to
enter larynx at greater cornu of
thyroid cartilage, Riddle’s triangle
is also called Beahrs triangle
Key Box 37.1B
Recurrent Laryngeal Nerve Anomalies
The nerve traverses through the gland in about 5–8%
of cases.
The nerve may be very closely adherent to the
posteromedial aspect of the gland.
Nerve not seen—may be far away in the tracheo-
oesophageal groove.
Nonrecurrent, recurrent laryngeal nerve is found in about
1 in 1,000 cases. The nerve has a horizontal course.
In 25% of the cases, it is within the ligament of Berry.
Fig. 37.3: Course of recurrent laryngeal nerve—gland is
mobilised. The branches of inferior thyroid are ligated (not the
main trunk)
1
Amelita Galli-Curci nerve was an opera singer whose SLN got injured resulting in voice changes. Often this nerve is referred to as Amelita Galli-
Section II • General Surgery
Curci nerve.
Fig. 37.4: Course of recurrent laryngeal nerve and origin
Thyroid Gland
397
Lymphatic Drainage of Thyroid
• Subcapsular lymphatic plexus drains into pretracheal
nodes (Delphic nodes means uncertain) and
prelaryngeal nodes which ultimately drain into lower
deep cervical nodes and mediastinal nodes (Fig. 37.5).
• The chief lymph nodes are middle and lower deep
cervical lymph nodes (Levels III and IV).
• Supraclavicular nodes and nodes in the posterior
triangle can also be involved in malignancies of the
thyroid gland, especially papillary carcinoma thyroid.
Histology (Fig. 37.6)
• Microscopically, it is divided into lobules.
• Each lobule has 20–40 follicles.
• Each follicle is lined by cuboidal epithelial cells.
• In the centre, colloid is present which is secreted from
epithelial cells in response to calcitonin.
• Parafollicular cells are present in the interfollicular
stroma.
requirement of iodine per day is 100–200 mg or 0.1 mg.
Sources of iodine are milk, dairy products and sea food
including fish.
Steps involved in the synthesis of these hormones
1. Iodide trapping from the blood into the thyrocyte is
the first step in the formation of T
and T4.
3
• Thiocyanates and perchlorates block this step.
2. Oxidation of iodide to inorganic iodine: This step
needs the enzyme peroxidase.
• Drugs which block this stage (thioamides) are
sulfonamide, PAS (para-amino-salicylic acid),
carbimazole and propylthiouracil.
3. Formation of iodotyrosines
• Iodine + Tyrosine = MIT (monoiodotyrosine) and
diiodotyrosine (DIT)
• This step is inhibited by thiourea group of drugs,
i.e. carbimazole.
4. Coupling reactions
• Coupling of two molecules of DIT results in T
one molecule of DIT and MIT results in T
and
4
.
3
• This stage is blocked by carbimazole.
5. Hydrolysis
• The hormones combine with globulin to form a
colloid-thyroglobulin. They are stored in the
thyroid gland and released as required by process
of hydrolysis.
is an important physiological hormone and is
• T
3
fast-acting (few hours). T
is a slow-acting hormone
4
and takes about 4–14 days to act.
Fig. 37.5: Lymphatic drainage
Fig. 37.6: Diffuse colloid goitre—acini lined by cuboidal follicular
cells with luminal colloid (Courtesy: Dr Laxmi Rao, Head,
Department of Pathology, KMC, Manipal)
PHYSIOLOGY
Tri-iodothyronine (T3) and thyroxine (T4) are the
hormones secreted by the thyroid gland. Dietary
THYROID FUNCTION TESTS
Serum T3 and T4 estimation is most commonly performed. Other tests are not commonly done and some
of them are obsolete (Table 37.1).
1. Serum T
• Most (80%) T
: Normal levels—1.5–3.5 nmol/L
3
is produced by deiodination of T
3
in the liver, muscle, kidney and anterior pituitary.
• T
is 3 to 4 times more potent than T4.
3
• The half-life of T3 is approximately 24 hours,
whereas half-life of T
Table 37.1 Levels of T3, T4 and TSH in some common
conditions
Disease T
• Thyrotoxicosis ↑↑ Suppressed or
toxicosis ↑↑ Normal Suppressed
• T
3
• Hypothyroidism Low or Low ↑
normal
is about 7 days.
4
3
T
4
TSH
undetect
able
4
Section II • General Surgery
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Manipal Manual of Surgery
• Free T3 (3 to 9 pmol/L) is most useful in confirming
the diagnosis of early hyperthyroidism, especially
in pregnancy wherein levels of free T
and free T
4
rise before total T4 and T3.
2. Serum T
: Normal levels—55 to 150 nmol/L
4
• They are measured by radioimmunoassay.
• In euthyroid state, T
is the predominant hormone
4
produced by the thyroid.
• Total T
gland. Both T
levels reflect output from the thyroid
4
and T4 increase cell metabolism,
3
normal growth, facilitate normal mental development and increase local effects of catecholamines.
• Free T
pmol/L). Free T
(ref range 12–28 pmol/L) and free T4 (3–9
3
estimates are not performed as a
4
routine screening in thyroid disease. Use of this
test is confined to cases of early hyperthyroidism
Graves’ disease where T
free T
tance to T
Free T
is raised. In patients with end organ resis-
4
, T4 levels are raised but TSH is normal.
4
is useful to confirm cases of early hyper-
4
thyroidism in which levels of both free T
total may be normal but
4
and T
3
rise before total T3 and T4.
3. Serum TSH (thyroid-stimulating hormone): 0.3–5
IU/ml of plasma. Table 37.1 shows the levels of T
T4 and TSH in a few common conditions.
4. Serum thyroglobulin (TG)
• It is produced by thyroid tissue only. Hence, the
levels should be low after total thyroidectomy.
• The most important use of this test is to monitor
patients after total thyroidectomy for well-
3
differentiated carcinoma.
• It is not normally released into circulation in large
amount but increases suddenly in thyroiditis,
Graves’ disease or toxic multinodular goitre (MNG).
5. Serum cholesterol: It is increased in hypothyroidism
and decreased in hyperthyroidism.
6. Thyroid autoantibody levels: More than 90% of the
patients with Hashimoto’s thyroiditis and 80% of
patients with Graves’ disease have antibodies which
are called ‘LATS’ (long-acting thyroid stimulator).
The detection of these antibodies helps in the
diagnosis of such cases and also to suspect these
diseases before clinical manifestation. These include
anti-TG, antithyroid peroxidase and thyroidstimulating immunoglobulin.
• Anti-TPO levels >25 µ/ml and anti-thyroglobulin
titres more than 1:100 are considered significant.
• TSH receptor antibodies are also present in Graves’
3
disease. They are largely produced within the
thyroid itself.
7. Thyroid scintigraphy (Table 37.2 and Fig. 37.7):
,
3
Uptake by both lobes.
8. Serum calcitonin: It is a sensitive marker for
medullary carcinoma thyroid. (0–4 pg/ml basal)
• CEA may also be used as an alternate screening
test for medullary carcinoma thyroid.
Table 37.2 Thyroid scintigraphy
Substance Dose Half-life Ideal case
131
I High dose radiation (500 mrad) Long 8–10 days Lingual thyroid, retrosternal
goitre; images are better.
123
I Low dose radiation (30 mrad) Shorter 8–10 hours Well-differentiated carcinoma
for bony metastasis.
99m
Tc (technetium) Lowest radiation (5 mCi) Shorter half-life Sensitive for nodal metastasis
6–8 hours Lingual thyroid.
Fig. 37.7
A Few Terminologies of Thyroid Disorders (Table 37.3)
Table 37.3 Nomenclature of certain thyroid diseases
• Ectopic thyroid • Thyroid tissue along the line of descent
Diagnosis by isotope scan or CT scan Example: Floor of the mouth, submental region, mediastinum
• Lingual thyroid • Swelling in the region of foramen caecum in tongue
Diagnosis by isotope scan or CT scan
• Dyshormonogenesis • Autosomal recessive condition with deficiency of peroxidase or dehalogenase
It is familial.
• Pendred’s syndrome • Dyshormonogenesis with congenital deafness
• Struma ovarii • Malignant ovarian teratoma containing thyroid tissue
• Jod Basedow’s disease (German word) • Excessive iodine given for hyperplastic goitre resulting in hyperthyroidism
Section II • General Surgery
(enzymes)
Thyroid Gland
399
CLINICAL EXAMINATION OF THYROID SWELLING
Diseases of the thyroid are very common and thyroid
swellings are very often common cases in an undergraduate and postgraduate clinical examination. Hence,
before discussing the various diseases of the thyroid
gland, various aspects of the “CLINICS” are discussed
in detail below.
COMPLAINTS—HISTORY TAKING
. Swelling: Long duration of thyroid swelling indicates
1
benign condition, e.g. multinodular goiter (MNG),
colloid goitre. Short duration with rapid growth
indicates malignancy, such as anaplastic carcinoma.
Majority of thyroid swellings do not produce pain.
2. Rate of growth: Usually slow-growing in benign
disease. If it is a rapid growth, it can be ‘de novo’
malignancy or malignancy developing in a benign
lesion, e.g. follicular carcinoma in MNG. Sudden
increase in the size of swelling with pain indicates
haemorrhage in the MNG (multinodular goitre).
3. Dyspnoea: Difficulty in breathing in a patient
with
goiter can be due to the following reasons (Key Box 37.2).
• Small goitre, rapid growth—anaplastic carcinoma
infiltrating the trachea.
• When lower border is not seen, retrosternal goitre.
• Hyperthyroidism causing arrhythmias leading to
congestive cardiac failure can cause dyspnoea and
orthopnoea.
• Long-standing MNG compresses on the tracheal
cartilages and produces pressure atrophy of
tracheal cartilages. This is called tracheomalacia.
4. Dysphagia is relatively uncommon because oeso-
phagus is a posterior structure and it is a fibromuscular tube.
5. Hoarseness of voice indicates malignancy. It always
occurs in carcinoma thyroid infiltrating the recurrent laryngeal nerve (never in benign diseases of
thyroid).
6. Toxic features suggestive of hyperthyroidism.
A. CNS symptoms are predominantly seen in Graves’
disease (primary thyrotoxicosis
—Key Box 37.3)
• Tremors of the hand
• Sweating
• Intolerance to heat
• Preference to cold
• Excitability
• Irritability
• Prominent eyes are observed by other persons.
Double vision, oedema of the conjunctiva can
be the presenting complaints in late cases.
Key Box 37.3
Graves’ Disease
Goitre
Ophthalmic symptoms
Irritability
Tremors
Restlessness
Excitability
Remember as GOITRE.
Key Box 37.2
Dyspnoea in Goitre—Causes
Infiltration of trachea Anaplastic carcinoma
Lower border not seen Retrosternal goitre
Tracheomalacia Long-standing MNG
Cardiac failure Secondary thyrotoxicosis
Fig. 37.8: Summary of history taking
B. Cardiovascular symptoms (CVS) are predomi-
nantly seen in secondary thyrotoxicosis. Even
though both forms of thyrotoxicosis produce palpitations, it is a significant complaint in multinodular
goitre with thyrotoxicosis (secondary thyrotoxicosis). Precordial chest pain and dyspnoea on
exertion are late manifestations of secondary
thyrotoxicosis (Summary, Fig. 37.8).
Section II • General Surgery
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Manipal Manual of Surgery
ON EXAMINATION
Inspection
1. The location of the swelling is in front of the neck,
extending from one sternomastoid to the other
sternomastoid, vertically from suprasternal notch to
the thyroid cartilage.
. The size and shape have to be mentioned.
2
3. Surface: Thyroid swellings can have the following
types of surfaces:
a. Smooth—adenoma, puberty goitre, Graves’
disease
b. Irregular—carcinoma of the thyroid
c. Nodular—multinodular thyroid
4. Borders are usually round.
5. Swelling moves up with deglutition because of the
following reasons (Key Box 37.4):
• Thyroid is enclosed by pretracheal fascia which is
condensed to form a ligament posteromedially
called ligament of Berry. These are pairs of liga-
ments attached above to cricoid cartilage. During
deglutition, the cricoid cartilage moves upwards
and with it, the thyroid gland (give the patient a
glass of water and check for movement with
deglutition). This action is by inferior constrictors.
• These muscles mainly do the function of swallow-
ing when food enters from pharynx to upper
oesophagus.
• It has two parts—thyropharyngeus arises from
thyroid cartilage and cricopharyngeus arises from
cricoid cartilage.
• When these muscles act, thyroid and cricoid
cartilage moves upwards. Thus, thyroid gland also
moves upwards.
• Inferior constrictors are supplied by vagus nerve.
These are thickest constrictor muscles.
• If there is restriction of movement, it can be
due to:
Malignancy with fixity to the trachea
–
– Retrosternal goitre
– Large goitre because of the size
– Previous surgery
6. Movement on protrusion of the tongue suggests
thyroglossal cyst. This test should be done when
there is a nodule or a cyst in the region of isthmus of
the thyroid gland. This test has no relevance in cases
of MNG or other thyroid swellings.
Palpation
It should be done from behind. First mention what parts
of thyroid gland are palpable.
. Size, shape, surface and border should be confirmed.
1
Local rise of temperature is a feature of toxic goitres.
Very large nodular surface is described as bosselated
surface (Fig. 37.9).
2. Consistency:
• Soft: Graves’ disease, colloid goitre.
• Firm: Adenoma, multinodular goitre.
• Hard: Carcinoma, calcification in the MNG.
. Confirm the movement with deglutition by holding
3
the thyroid gland.
4. Intrinsic mobility of the gland is very much restricted
in carcinoma because of infiltration into prevertebral
fascia behind or a malignant nodule which starts
infiltrating trachea. Otherwise, thyroid gland has
hardly any intrinsic mobility. When you try to move
it moves with the trachea.
5. Sternomastoid contraction test is done when only
one lobe is enlarged. In this situation, the examiner
keeps the hand on the side of the chin, opposite the
side of the lesion and asks the patient to push his
hand against resistance. If the gland becomes less
prominent (as with thyroid swellings), it indicates
the swelling is deep to the sternomastoid muscle.
Key Box 37.4
Swellings which Move Upwards with Deglutition
Thyroid swellings
Subhyoid bursitis
Pretracheal and prelaryngeal lymph nodes
Thyroglossal cyst
Laryngocele
Section II • General Surgery
Fig. 37.9: Endemic goitre of 35 years duration turned into
multinodular goitre. She presented with 3 months history of rapid
increase in the size of the swelling. She underwent total
thyroidectomy. Final histopathology report was follicular
carcinoma thyroid. Observe large nodular surface—
bosselations. (Courtesy: Dr Chidananda KV, Professor and Head,
Department of surgery and Dr Gopinath Pai, Professor,
Department of Surgery, KVG Medical College, Sullia, Dakshina
Kannada, Karnataka. MBBS exam case 2007)
Thyroid Gland
401
6. Chin test (neck fixation test) is classically done in
multinodular goitre, wherein both lobes are enlarged.
The patient is asked to bend the chin downwards
against resistance. This produces contraction of both
sternomastoids and strap muscles and the gland
becomes less prominent (Fig. 37.10).
7. Special tests or methods of examination of thyroid
gland:
a. Crile’s method is indicated when there is a doubt-
ful nodule. Keep the thumb over the suspected
area of the nodule and ask the patient to swallow.
The nodularity is appreciated better with this test
(Fig. 37.11).
b. Lahey’s method of examination of thyroid can be
done from front as well as behind. In order to
palpate the right lobe, push the gland to the right
side and feel the nodules in the posteromedial
aspect of the gland. The lobe becomes more prominent and thus nodules are appreciated better.
c. Pizzillo’s method is indicated in obese patients
especially short-necked individuals. The patient
is asked to clasp her hands and press against
her occiput with head extended. Thyroid gland
becomes more prominent and thus, palpation
becomes better.
d. Kocher’s test: If gentle compression on lateral lobes
produces stridor, it is described as positive. This
1
is due to scabbard
trachea. Long-standing multi-
nodular goitres causing tracheomalacia and
collapse after thyroidectomy resulting in stridor.
8. Position of trachea: In cases of solitary nodule
confined to one lobe, trachea is deviated to the opposite side. However, in cases of multinodular goitres,
trachea need not be deviated because of symmetrical
enlargement of both lobes.
9. Palpation of lymph nodes in the neck. If lymph
nodes are significant, it indicates papillary carcinoma
of the thyroid.
10. Palpation of common carotid artery: Draw a line
from mastoid process to sternoclavicular joint. Then
draw a horizontal line from upper border of thyroid
cartilage. The point where these two lines meet is
the site of bifurcation of common carotid artery. This
artery should be palpated below this point, against
tubercle on the transverse process of cervical 6th
vertebra—called carotid tubercle or Chassaignac
tubercle. The carotid artery can be massaged against
this tubercle to relieve the symptoms of supraventricular tachycardia.
• In large multinodular goitres, the artery may be
pushed laterally. Hence, pulsations are felt in the
posterior triangle. Carcinoma of the thyroid
engulfs the carotid sheath. Consequently, pulsations may be absent. Absent carotid artery
pulsation is called Berry sign positive. Since the
lumen is not narrowed, superficial temporal artery
pulsations are felt normally.
Percussion
Percussion over the sternum gives a resonant note
in normal cases. In retrosternal goitres, it gives a dull
note.
Auscultation
• It should be done in the upper pole because of
following reasons: Superior thyroid artery is a direct
branch of external carotid artery. It is more superficial
than inferior thyroid artery.
• Presence of thrill and bruit are the features of toxic
goitre.
Systemic Examination
This includes CNS and eye signs, as in Graves’ disease,
examination of skeletal system to rule out metastasis
as in carcinoma of the thyroid, and examination of
cardiovascular system in cases of toxic goitre. These
have been dealt with in detail in the corresponding
topics. Deep tendon reflexes also have to be elicited—
there is a slow relaxation phase in hypothyroidism.
Diagnosis
You need to confirm it is thyroid gland (Key Box 37.5)
and to mention the disease and functional status. It
Fig. 37.10: Chin test—neck
flexion test—thyroid swellings
become less prominent
1
Scabbard is a sheath for holding a sword or other large blade (it is narrow and curved).
Fig. 37.11: Crile’s method to
detect nodule wherein thumb
is used
should be noted that the neural tumours arising from
vagus nerve can present in the same location, but it will
not move with deglutition.
Section II • General Surgery
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Manipal Manual of Surgery
Key Box 37.5
Anatomical Features of the Thyroid Gland
1. Thyroid gland is in front of the neck
2. Deep to pretracheal fascia
3. Moves up with deglutition
4. Butterfly-shaped when whole gland is enlarged
GOITRE
DEFINITION
Diffuse enlargement of the thyroid gland is described
as goitre. (It is derived from the Latin word, Guttur =
the throat.)
Classification of Goitre
I. Simple goitre
• Puberty goitre
• Colloid goitre, iodine deficiency goitre (Fig. 37.12)
• Multinodular goitre
II. Toxic goitre
• Graves’ disease; diffuse toxic goitre
• Secondary thyrotoxicosis in multinodular goitre
• Toxic nodule; other causes.
III. Neoplastic goitre
• Benign adenoma (follicular adenoma)
• Malignant tumours: They are further classified as
follows:
A. Primary
• Well-differentiated carcinoma
– Papillary carcinoma, follicular carcinoma
• Poorly differentiated carcinoma
– Anaplastic carcinoma
• Arising from parafollicular cells
– Medullary carcinoma
• Arising from lymphatic tissue
– Non-Hodgkin’s lymphoma.
B. Secondary (Metastasis)
• Malignant melanoma, renal cell carcinoma,
breast carcinoma produce secondaries in the
thyroid, due to blood spread.
IV. Thyroiditis
• Granulomatous thyroiditis
• Autoimmune thyroiditis
• Riedel’s thyroiditis.
V. Other rare causes of goitre
• Acute bacterial thyroiditis
• Thyroid cyst
• Thyroid abscess
• Amyloid goitres
Multinodular goitre, solitary thyroid nodule, malignant goitres,
and puberty goitres are common causes of goitre. Bacterial
thyroiditis is rare. Riedel’s thyroiditis is very rare.
MULTINODULAR GOITRE
• A multinodular goitre is the end-stage result of
diffuse hyperplastic goitre. Excessive metabolic
demands cause an excessive enlargement of the
thyroid. Therefore, it is common in women.
• Metabolic demands increase during puberty. A goiter
appearing during that period is called puberty goitre.
A goitre can develop during pregnancy and is called
pregnancy goitre. Both of them are physiological but
may eventually develop into multinodular goiter
(MNG) (Fig. 37.13).
SU22.2: Describe the etiopathogenesis of thyroidal
swellings.
Aetiopathogenesis
Multinodular goitre occurs due to continuous stimulation by TSH secreted from the anterior pituitary.
Fig. 37.12: Observe smooth surface —colloid goitre of 15 years
duration
Section II • General Surgery
Fig. 37.13: Multinodular goitre showing nodules
Thyroid Gland
403
1. Puberty goitre, pregnancy goitre
• It is seen in girls at puberty or during pregnancy
when the metabolic demands are high and the
production of T
, T4 are comparatively normal.
3
Due to feedback mechanism, TSH levels increase,
which stimulates thyroid gland and causes diffuse
hypertrophy and hyperplasia.
• This is also called physiological goitre and can
be treated by giving tablet thyroxine (T
100 micrograms/day to suppress TSH.
• Goitre may disappear, if treatment is given in the
stage of diffuse hypertrophy.
2. Iodine deficiency goitre
• Daily iodine requirement is about 100–125 μg.
• Common in hilly/mountainous or low-lying areas
because of decreased iodide content of water. This
causes iodine deficiency goitre mediated by the
same feedback mechanism.
• This is treated with iodised salt (which is used in
food) and iodine—containing preparations.
• If the iodine deficiency status continues for a long
time, it results in accumulation of colloid material
in the gland and causes colloid goitre.
• All these three types of goitre, if left untreated, will
change to multinodular goitre (Fig. 37.14).
– Stage I: Stage of diffuse hypertrophy and hyper-
plasia of thyroid.
) 50 to
4
– Stage II: Due to fluctuating levels of TSH
because of pregnancy, lactation, menstruation,
etc. Some areas in thyroid are overstimulated
and are converted to active follicles.
– Stage III: The active follicle ultimately under-
goes necrosis and many such necrosed follicles
join to form a nodule. Many such nodules form
a multinodular goitre. Nodules contain necrosed
tissue, i.e. inactive tissue. The internodular
tissue is active.
3. Goitrogens such as cabbage (contains thiocyanates),
drugs such as amiodarone and sulfonamides, cause
goiter by preventing oxidation of iodide to iodine.
Excess iodides inhibit organic binding of iodine and
produce goitre.
4. Dyshormonogenesis (see Table 37.3)
Clinical Features
• Common in females. Female: male ratio is 10 : 1. Seen
in the age group of 20–40 years.
• Long duration of swelling in front of the neck,
dyspnoea due to tracheomalacia and dysphagia are
the presenting features. The gland is nodular, firm
in consistency and both the lobes are enlarged. Hard
areas may suggest calcification and soft areas,
necrosis.
• Sudden increase in size with pain is mainly due to
haemorrhage in a nodule.
Fig. 37.14: Pathogenesis of MNG
Section II • General Surgery