This presentation is about the Thyroid Gland, the anatomy, the physiology, and the different pathology.

1. The Thyroid Gland

2.  Diseases of the thyroid predominantly
affect females
 Common, affecting 5 % of the
population
 Thyroid axis is involved in the
regulation of cellular differentiation
and metabolism in virtually all
nucleated cells

3. Classification of thyroid
disease
Primary Secondary
Hormone excess Graves’ Disease
Multinodular goitre
Adenoma
Subacute thyroiditis
Pituitary TSHoma
Hormone deficiency Hashimoto’s thyroiditis
Atrophic
hypothyroidism
Hypopituitarism
Hormone
hypersensitivity
-
Hormone resistance Thyroid hormone
resistance syndrome
5’-monodeiodinase
deficiency
Non-functioning
tumours
Differentiated
carcinoma
Medullary carcinoma

4. ENLARGEMENT OF THE
THYROID GLAND (GOITRE)
 Goitre is a visible or palpable enlargement of the
thyroid.
 Clinical features:
- The swelling appears in the lower part of the
neck and retains the shape of the normal gland.
- It characteristically moves upwards on
swallowing because of the gland's attachment to
the trachea.
 'Physiological' enlargement - transient
enlargement may occur during puberty or
pregnancy.

5. NON-TOXIC NODULAR
GOITRE
Etiology :
 This common disease occurs
endemically in areas of iodine deficiency,
but can be sporadic or a reaction to
drugs.
 occurs much more commonly in females.
 In the past, lack of iodine in the diet was
a common cause of thyroid enlargement,
but 'endemic goitres' are now rare
because table salt is iodized.
 In areas of the world where iodine intake
cannot be guaranteed, iodized oil
emulsion can be injected.

6. Pathology
 In iodine deficiency, the gland initially
enlarges diffusely as the follicles fill with
colloid.
 Later, multiple nodules develop, some of
which contain abundant colloid; others show
degenerative changes, with the formation of
cysts, areas of old and new haemorrhage,
and even calcification.
 The goitre varies greatly in size, from little
more than normal to weighing several
hundred grams.
 The whole gland may be involved, or the
changes may be confined to one lobe.

7. Clinical Features
 Most multinodular goitres are
asymptomatic.
 Others cause tracheal compression
and dyspnoea, particularly when they
extend behind the sternum
(retrosternal goitre).
 Esophageal compression can cause
dysphagia.

8.  Very rarely, bleeding into a nodule may
cause pain and rapid enlargement and,
in the case of retrosternal goitre,
respiratory distress.

 The thyroid is visibly enlarged and
multiple nodules are usually palpable.
 Sometimes only one nodule is palpable,
giving the erroneous impression of a
solitary nodule

9. Investigations
 In the case of retrosternal goitre, plain films of
the thoracic inlet may reveal tracheal
deviation .
 Only a CT scan will show tracheal
compression.
 The presence of stridor should alert the
physician to the presence of compromise of
the tracheal lumen .
 T3, T4 and TSH are usually normal.
 TAA, to diferrentiate from autoimmune
thyroiditis.
 Isotope scans are most often unhelpful.

10. Management
 The administration of thyroxine
occasionally prevents further
enlargement by suppressing TSH
secretion, but regression of the goitre is
unusual.
 Large goitres and those causing
symptoms of compression require total
or subtotal thyroidectomy.
 Some patients request surgery for
cosmetic reasons.

11. THYROTOXIC GOITRE
 Diffuse thyroid enlargement can result
from stimulation by TSH or TSH-like
proteins, resulting in increased
production of T3 and T4 and
thyrotoxicosis.
 However, most goitres occur in
individuals who have normal function.
 The combination of goitre and
hyperfunction is an indication for surgical
treatment.

12. THYROIDITIS
Subacute thyroiditis (de Quervain's
disease)
 This rare condition is associated with an
influenza-like illness, during which there
is painful diffuse swelling of the gland.
 Thyroid antibodies may appear in the
serum.
 The disease may be due to a viral
infection and usually resolves, although
occasionally it runs an intermittent
course.

13. Autoimmune thyroiditis
(Hashimoto's disease)
Etiology
 This condition is believed to be due to
the destruction of thyroid follicles by
immunocompetent lymphocytes.
 Antibodies are detected in the serum
against thyroglobulin, thyroid cell
cytosol and microsomes.
 Histologically, there is marked
lymphocytic infiltration around
destroyed follicles.

14. Clinical features
 The patient is usually euthyroid, but
thyrotoxicosis can occur.
 In the long term, the patient becomes
hypothyroid.
 Post-menopausal women are most
commonly affected (female:male ratio 10:1).
 The thyroid is diffusely enlarged and firm.
 A nodular form may be confused with
multinodular goitre.
 Lymphoma may occur in a thyroid that has
been affected by long-standing Hashimoto's
disease.

15. Investigations
 The diagnosis depends on
demonstrating high titres of circulating
antithyroid antibodies, particularly to
microsomal components of the follicle
cells.
 Biopsy for cytology helps to confirm
the diagnosis.

16. Management
 Thyroxine causes regression of small
goitres, but thyroidectomy is needed
when a large goitre is causing
compression symptoms.
 Surgery can be difficult because of the
firm nature of the gland and inflammation
of the surrounding structures.
 There is a higher than normal risk of
damage to the recurrent laryngeal
nerves or parathyroid glands.

17. Riedel's thyroiditis
 In this very rare condition the thyroid is
replaced by dense fibrous tissue,
resulting in a firm painless swelling
and tracheal compression.
 The cause is unknown.
 Surgical decompression of the trachea
may be required.

18. Solitary Thyroid Nodules
 Slow-growing and painless clinically
'solitary' nodules
 Common
 50% are part of a multinodular goitre.
 Of the true solitary nodules, half are
benign adenomas and the rest are
cysts or differentiated cancers.

19. Investigations
 The pivotal diagnostic test is fine-
needle aspiration cytology,
complemented by ultrasonography,
isotope scans and thyroid function
tests.
 Cysts can be aspirated and, provided
that they do not refill and that the
cytology is negative for neoplastic
cells, they need not be removed.

20.  Very rarely, a cyst contains a carcinoma
(often papillary) within its wall, and blood-
stained aspirate or a residual swelling after
aspiration should raise this possibility.
 A cytopathologist cannot distinguish between
a follicular adenoma and follicular carcinoma;
this can only be achieved on definitive
histopathology by looking for capsular or
vascular invasion.
 Surgery is needed if aspiration reveals a
follicular neoplasm.

21. OTHER FORMS OF
NEOPLASIA
 All forms of thyroid cancer can
produce a goitre.
 Lymphoma and anaplastic tumours
may cause diffuse thyroid swellings.
 Medullary and follicular tumours are
often solitary swellings.

22. HYPERTHYROIDISM
 Thyrotoxicosis results from the
overproduction of T3 and T4 and,
because of the feedback mechanism,
serum TSH levels are reduced or
undetectable.
 The three conditions that may produce
thyrotoxicosis are primary
thyrotoxicosis (Graves' disease), toxic
multinodular goitre and toxic

23. PRIMARY THYROTOXICOSIS
(GRAVES' DISEASE)
Pathophysiology :
 This condition accounts for 75% of
cases.
 It is an autoimmune disease in which
TSH receptors in the thyroid are
stimulated by circulating thyroid-
stimulating immunoglobulins (TSI).
 The gland is uniformly hyperactive,
very vascular and usually
symmetrically enlarged, although not

24.  Histologically, there is marked
epithelial proliferation, with papillary
projections into follicles devoid of
colloid.
 TSI can cross the placental barrier, so
that neonatal thyrotoxicosis can occur.

25. Clinical features
 The patient is usually a young female
(male:female ratio 1:8) and the
condition can be familial.
 The thyroid is usually moderately and
diffusely enlarged and soft, and
because of its vascularity a bruit may
be audible.
 High circulating levels of T3 and T4
increase the basal metabolic rate and
potentiate the actions of the
sympathetic nervous system.

26. Metabolic effects
 The patient feels hot at rest and is
intolerant of warmth.
 The skin is moist and warm because
of peripheral vasodilatation and
excess sweating.
 Weight loss is the rule, despite an
increased appetite.
 Cardiac output is increased to meet
the metabolic demands.

27. Sympathetic effects
 Tachycardia is present, even during
sleep.
 Palpitations can be troublesome, and
cardiac irregularities and arrhythmias
(especially atrial fibrillation) are
common in older patients.
 The hands exhibit a fine tremor.

28.  The upper eyelids are retracted (the
levator palpebrae superioris has some
non-striated muscle which is
innervated by the sympathetic nervous
system) and there is lid lag.
 Gastrointestinal motility is increased.
There is general hyperkinesia; anxiety
and psychiatric disturbance may
occur.

29. Other features
 Exophthalmos is usual but not
invariable.
 Ophthalmoplegia, pretibial
myxoedema, proximal muscle
myopathy and finger clubbing are
sometimes present.
 Menstrual irregularity and infertility can
occur.

30. Diagnosis
 The diagnosis is usually obvious
clinically, although in patients with
anxiety, distinction from neurosis can
be difficult.
 Raised T3 and T4 levels, coupled with
low TSH levels, are confirmatory.
 The TSH response to intravenous
injection of TRH is absent owing to
atrophy of the TSH-producing cells of
the pituitary.

31. Management
Antithyroid drugs:
 These drugs block the incorporation of iodine
into tyrosine and so prevent the synthesis of
T3 and T4.
 Carbimazole, given in full blocking doses (30-
60 mg daily in four divided doses), can render
the patient euthyroid within 4-6 weeks.
 However, up to 60% of patients will relapse
within 2 years of stopping treatment.

32. Radioactive iodine :
 Many consider this to be the treatment of
choice.
 As long as it is not used in pregnancy, the
risks of genetic damage are minimal in both
patients and their offspring.
 If ablative doses of iodine are used, patients
require thyroxine replacement, but can lead
an otherwise normal life with little risk of
recurrence.

33. Surgery :
 Thyroidectomy is a highly successful
form of treatment for many patients,
especially younger ones.
 In experienced hands, operative
mortality and morbidity are low.
 Patients may be cured by surgery, and
recurrence is usually due to the removal
of insufficient glandular tissue.

34.  Hypothyroidism occurs in 50% or
more of patients, and low T3 and T4
levels with high TSH levels persisting
for more than 6 months signal the
need for lifelong thyroid hormone
replacement.
 Before surgery, patients must be
rendered euthyroid with antithyroid
drugs.
 Iodine can be given before surgery to

35.  Beta-adrenergic blocking drugs can be
used as an alternative means of
countering the effects of thyrotoxicosis
before operation.
 They block sympathetic overactivity and
make the gland less vascular.
 Cardiac failure, obstructive airways
disease and diabetes (where they may
mask hypoglycaemic symptoms) are
contraindications to the use of β-
blockers.

36.  Propranolol is given in a dose of 40-80
mg 6-hourly, the aim being to reduce the
pulse rate to below 80 beats per minute
(bpm).
 Long-acting preparations may be
preferred.
 The drug is continued on the morning of
operation and for 7 days thereafter to
avoid 'thyroid storm' or 'thyrotoxic crisis'.
 Excessive sweating or tachycardia after
operation is an indication to increase the
dose.
 Increasingly, total thyroidectomy is
performed in preference to subtotal.

37. TOXIC MULTINODULAR
GOITRE AND TOXIC
ADENOMA
Pathophysiology
 A toxic multinodular goitre is
responsible for thyrotoxicosis in about
25% of patients.
 There is usually a long-standing non-
toxic goitre in which one or more
nodules become hyperactive and
begin to function independently of
TSH levels.

38.  A single functioning adenoma is a rare
cause of thyrotoxicosis (1-2% of
patients).
 The adenoma secretes thyroid
hormones autonomously, TSH
secretion is completely suppressed,
and the remainder of the gland is non-
functional.

39. Clinical features
 Toxic multinodular goitre is more
common in older women
 cardiac complications such as
arrhythmias are particularly frequent
 exophthalmos is rare
 patients with a toxic adenoma hardly
ever have exophthalmos,
ophthalmoplegia or myopathy.

40. Diagnosis
 In a toxic multinodular goitre, the isotope
scan demonstrates one or more areas of
increased uptake. In toxic adenoma, the
nodule is 'hot' and the remainder of the
gland is 'cold'.
Management
 Treatment consists of removal of the
hyperfunctioning glandular tissue by
subtotal thyroidectomy (multinodular
goitre) or lobectomy (toxic adenoma), or
radioiodine.

41. Hypothyroidism
 Cretinism(fetal/infantile
hypothyroidism)
- Due to complete or near complete
failure of thyroid development.
- In endemic areas

42. MALIGNANT TUMOURS OF
THE THYROID
 Thyroid cancer accounts for less than
1% of all forms of malignancy.
 As with all thyroid disease, females are
more often affected (male:female ratio
1:3).
 The two main types of thyroid carcinoma
are papillary (50%) and follicular (30%),
with the remainder comprising medullary
carcinoma, anaplastic carcinoma and
lymphoma.
 The incidence of thyroid cancer is
increased by exposure to ionizing
radiation.

43. PAPILLARY CARCINOMA
 Clinical features
 This disease typically presents as a
solitary thyroid nodule in patients aged
30-50 years.
 Lymph node metastases are much less
common than haematogenous spread
 20% of patients have deposits in the
lungs, bone or liver. Histologically,
malignant cells are arranged in solid
masses with rudimentary acini.
 Vascular and capsular invasion
characterize this neoplasm and
distinguish it from a benign follicular
adenoma.

44.  Management
- total thyroidectomy with preservation of
the parathyroids.
- therapeutic doses of radioiodine are
given.
- T4 is administered routinely to suppress
TSH secretion.
- Plasma thyroglobulin levels should be
undetectable after surgery and
radioiodine therapy.
- Subsequent detection of thyroglobulin
indicates recurrent disease, the disease
is more aggressive than papillary
carcinoma and the 10-year survival rate
is 50%.

45. ANAPLASTIC CARCINOMA
 Clinical features:
-These rapidly growing, highly
malignant tumours tend to occur in
older patients.
- Local invasion may involve the
recurrent laryngeal nerve(s) and
cause hoarseness, or compress the
trachea and cause dyspnoea and
stridor, and/or compress the

46.  Invasion of the cervical sympathetic
nerves may cause Horner's syndrome
(contraction of the pupil,
enophthalmos, narrowing of the
palpebral fissure and loss of sweating
on the face and neck).
 Pulmonary metastases are common.
 Death usually occurs within 6 months
of diagnosis.

47. Management
 Resection is rarely possible but
surgery can relieve tracheal
compression.
 Radiotherapy and chemotherapy are
of marginal value.

48. MEDULLARY CARCINOMA
 Clinical features
-This tumour arises from the parafollicular C
cells.
-There is hard enlargement of one or both
thyroid lobes.
-50% of patients the cervical lymph nodes are
involved.
-The tumour may occur sporadically or as part
of an inherited multiple endocrine neoplasia
(MEN) syndrome type II (Sipple's syndrome).

49.  Calcitonin levels are elevated, and can
be used to monitor progress and screen
relatives.
 The gene causing the inherited form of
this tumour is the Ret proto-oncogene,
and the finding of this mutation allows
the diagnosis to be made at any age.
 Prophylactic thyroidectomy for affected
children is recommended from the age of
5 years in MEN IIa, but at 1 year for
MEN IIb.

50. Management
 Treatment consists of total thyroidectomy
and dissection of the lymph nodes in the
central compartment of the neck.
 Medullary carcinoma in MEN IIb
syndrome is particularly aggressive, and
those affected rarely live beyond 30-40
years of age.
 Other forms-for example, pure inherited
medullary thyroid cancer occurring
without other endocrine tumours-can be
very indolent.

51. Lymphoma
 Primary lymphoma of the thyroid is a
rare complication of autoimmune
thyroiditis.
 It can also occur as a primary tumour
that originates in an otherwise normal
gland.
 It is amenable to treatment by
radiotherapy and chemotherapy, but
patients often require core biopsy of the
gland to characterize the type of
lymphoma.

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