Surgery lecture on Benign Thyroid Diseases as a part of General Surgery curriculum of undergraduate medical students.

1. Thyroid: Basics

2. Development

3. Embryology

4. Embryology (contd.)
 Week 3 – Thickening in the floor
between first and second pharyngeal
pouches (later known as foramen
caecum at junction of ant 2/3rd and
posterior 1/3rd of tongue)
 Week 4 – Evagination of endoderm
ventrally into the mesoderm to form
thyroid diverticulum

5. Embryology (contd.)
 Week 5 – formation of thyroglossal
duct and bifurcation of the tip to for
lateral lobes and isthmus
 Week 6 – Growth of duct and
migration of thyroid gland downward
in close proximity or through hyoid
bone
 Week 7 – Gland reaches the final
position in relation to the larynx and
trachea

6. Embryology
(contd.)

7. Embryology
(contd.)

8. Anatomy

9. Surface
Anatomy

10. Location
 Location: lower part of
the front and side of
the neck opposite to
the C5, C6, C7 and T1
vertebrae.
 Each lateral lobe
extends upwards to
oblique line of thyroid
cartilage and below
up to the 5th or 6th
tracheal ring.
 The isthmus extends
across the midline in
front of the 2nd, 3rd and
4th tracheal ring.

11. Parts
 Lateral lobes
 right and Left
 located in between trachea &
oesophagus medially and carotid
sheath laterally
 Isthmus – connects two lateral lobes
 Pyramidal lobe – upward extension at
junction of isthmus to left lobe, seen in
30% individuals

12. Capsules
 True capsule
 Condensation of connective tissue of the
gland
 False/surgical capsule
 From the pre-tracheal layer of deep
cervical fascia
 Ligament of Berry
 Pre-tracheal fascia is thickened at the
posteromedial aspect of the lobes and
connects the gland to cricoid cartilage

14. Arterial Supply
 Superior thyroid artery
 from external carotid
artery
 Inferior thyroid artery
 from thyrocervical
trunk of subclavian
artery
 Thyroid ima artery
 in 10% population
 from brachiocephalic
trunk

15. Venous
Drainage
 Superior thyroid veins
 to Internal Jugular
Vein
 Middle thyroid veins
 to Internal Jugular
Vein
 Inferior thyroid veins
 to left
brachiocephalic trunk

16. Nerves in
close relation
1. EBSLN
 External branch of
Superior Laryngeal
Nerve
 Lies deep to Superior
Thyroid Artery near
the superior pole of
thyroid
 Highly variable
anatomy

17. Nerves in close
relation (contd.)
2. RLN
 Recurrent Laryngeal
Nerve
 Ascends posterior to
the gland in tracheo-
oesophageal groove
 In close relation to
Inferior Thyroid Artery

18. Nerves in
close relation
(contd.)

19. Physiology

20. Hormones
 2 important thyroid hormones:
 Thyroxine (T4)
 Triiodothyronine (T3)
 Secreted by Follicular cells.
 Having significant effect on the metabolic rate of the
body.
 Calcitonin
 Secreted by Parafollicular cells
 Important hormone for Ca2+ metabolism &
homeostasis

21. Synthesis
of Thyroid
Hormones

22. H-P-T Axis

23. Thyroid Function Tests

24. Thyroid Investigations and
Thyroid Nodule

25. Investigations

26. Thyroid Function Tests
 S. TSH
 can be measured accurately down to very low serum concentrations with an
immunochemiluminometric assay
 interpretation of deranged TSH levels depends on knowledge of the T3 and T4
values

27. Thyroid Function Tests(contd.)
 Serum T4 and T3
 In blood, most of the hormone is bound to serum proteins: albumin, thyroxine-
binding globulin (TBG) and thyroxine-binding prealbumin (TBPA)
 Biologically inactive
 Reflects the output of the gland
 Levels – T4: 55-150 nmol/litre, T3: 1.2-3 nmol/litre
 Free T4 and T3
 Unbound form and biologically active
 Concentration of free T4 and T3 are 0.03% and 0.3% of the total circulating
hormones, respectively
 Single best test for assessment of hyperthyroidism
 Levels – T4: 8-26 nmol/litre, T3: 3-9 nmol/litre

28. Thyroid Function Tests(contd.)
 Auto-antibodies
 Serum levels of antibodies against thyroid components are useful in
determining the cause of thyroid dysfunction and swellings
 TRAbs:
 stimulatory action on TSH receptors present over follicular cells
 longer duration of action than TSH (16–24 hours versus 1.5–3 hours)
 responsible for Grave’s disease
 Anti-TPO and anti-TG antibodies:
 antibodies against thyroid peroxidase and thyroglobulins are seen in auto-immune
thyroiditis
 may be associated with thyroid toxicity, failure or euthyroid goitre

29. Ultrasound
 The workhorse investigation in thyroid
disease for the surgeon.
 Not only can the characteristics of the
gland substance be quantified, but
the presence and features of thyroid
nodules can be described.
 Number, size, shape, margins,
vascularity and microcalcifications –
predict the risk of malignancy within a
specific nodule

30. Ultrasound
(contd.)
 Regional lymphatics,
particularly in the
lateral neck can be
assessed accurately for
the presence of
metastatic deposits.
 During ultrasound, fine
needle aspiration
(FNA) can be
performed more
accurately than free-
hand techniques allow.

31. Cross-sectional Imaging
 When metastatic disease is detected cross-sectional imaging is required
to fully stage the disease.
 Retrosternal extension, which can often be predicted on plain chest x-ray,
also requires more advanced techniques to determine the extent
adequately prior to considering management.
 Computed Tomography (CT)
 For most of these indications, the imaging modality of choice is computed
tomography (CT).
 Contrast enhanced CT is useful for determining the extent of airway invasion
 Magnetic Resonance Imaging (MRI)
 Superior at determining the presence of prevertebral fascia invasion.

32. FNAC
 Fine needle aspiration
cytology
 Investigation of choice
for conclusive
histological diagnosis
 Results should be
reported using
standard terminology
 Bethesda system used
for reporting and
decide further
management

33. FNAC (contd.)
 In Bailey and Love’s Short Practice of
Surgery, 27th edition
 Followed in United Kingdom

34. Radio-isotope
scanning
 Allows assessment of function of thyroid
gland and any nodule within it
 Isotopes used:
 Iodine-123 (123I) – best
 Technetium-99m (99mTc) – cheaper
 Its principal value is in the toxic patient
with a nodule or nodularity of the thyroid.
 NOTE: Iodine-131 is used for therapeutic purposes

35. Radio-isotope
scanning (contd.)
 Differentiate between:
 toxic nodule with suppression of the
remainder of the gland, and
 toxic multinodular goitre with several areas
of increased uptake
 Whole-body scanning is used to
demonstrate metastases
 however, metastatic thyroid cancer tissue
cannot compete with normal thyroid
tissue in the uptake of iodine

36. Congenital
disorders

37. Ectopic
Thyroid
 Presence of thyroid
tissues in locations
other than normal site
 May be found
anywhere in the line of
descent of thyroglossal
duct as well as in
anterior mediastinum

38. Thyroglossal
Cyst
 Thyroglossal duct
descends from the
base of the tongue
towards lower neck to
the level of second
and third tracheal rings
 Failure of obliteration
leads to cyst formation
 M/C site – Subhyoid
 Rarely, may be the
only functioning thyroid
tissue in the body

39. Thyroglossal Cyst (contd.)
 Clinical features:
 Mostly in children but may also present in
adults
 Almost always arise in the midline but may
lie slightly to one side of the midline
 Moves upwards on swallowing and with
tongue protrusion
 May become infected and rupture onto
the skin of the neck presenting as a
discharging fistula

40. Thyroglossal Cyst (contd.)
 Treatment:
 Excision of the whole thyroglossal tract
 removal of the body of the hyoid bone
 the suprahyoid tract through the tongue
base
 with a core of tissue around it
 Known as Sistrunk’s operation and prevents
recurrence
 Most notably from small side branches of
the thyroglossal tract
 Excision not done if only thyroid tissue

41. Thyroglossal Fistula
 Follows:
 infection of thyroglossal cyst
 inadequate excision of the cyst
 Clinical features:
 Presents with serous discharge
 Recurrent infection is common and
discharge may become purulent
 Hood sign – opening is indrawn and
overlaid by fold of skin
 Peculiar crescentic appearance
 Treatment
 Sistrunk operation

42. Thyroid Nodules

43. Terminology
 Solitary nodule:
 A discrete swelling in an otherwise
impalpable gland
 70% of nodules are solitary
 Dominant nodule:
 Distinctly palpable swelling in a gland with
clinical evidence of goitre or multiple
nodules
 30% of palpable nodules have other
nodules on imaging

44. Pathology
 Causes:
 Adenomas
 Carcinomas
 Thyroid cyst
 Thyroiditis
 Types:
 Hot – Autonomous toxic nodule
 Warm – Normally functioning nodule
 Cold – Non-functioning nodule

46. Thyroid Swellings

47. Classification

48. Thyroiditis

49. Hashimoto’s Thyroiditis
 Similar to chronic lymphocytic thyroiditis
 Autoimmune condition associated with raised titres of thyroid antibodies
directed against
 Thyroid peroxidase (Anti-TPO)
 Thyroglobulin (Anti-TG)
 Aka struma lymphomatosa, because thyroid tissue gets replaced by
lymphoid tissue
 M/C inflammatory disorder of thyroid and leading cause of
hypothyroidism

50. Hashimoto’s Thyroiditis (contd.)
 Pathology:
 Thyroid tissue is progressively destroyed
by cytotoxic T-lymphocytes and
autoantibodies
 Initially hyperplasia, then fibrosis and
eventually gland is diffusely infiltrated
by lymphocytes and plasma cells
 Characteristic finding, Hürthle or
Askanazy cells – abundant eosinophilic,
granular cytoplasm

51. Hashimoto’s Thyroiditis (contd.)
 Clinical features:
 Presents as minimal or moderate goitre
 Painful, firm, tender and smooth
 may be diffuse or
 nodular with a characteristic ‘bosselated’ feel
 Hormone status
 Initially, mild hyperthyroidism (hashitoxicosis) – destruction of gland leads to
release of pre-formed hormones
 Later, hypothyroidism – which is permanent

52. Hashimoto’s Thyroiditis (contd.)
 Investigations:
 Elevated TSH, reduced T4 & T3 levels
 Presence of thyroid antibodies, specially anti-TPO antibody
 In case of doubt, FNA confirms lymphocytic infiltration
 Treatment:
 Hormone replacement – oral L-thyroxine tablets
 Surgery – only if
 suspicion of malignancy
 large goitre causing compressive symptoms
 cosmetic reasons

53. De Quervain’s Thyroiditis
 Aka Granolumatous/Subacute/Viral thyroiditis
 May follow a viral infection – usually upper respiratory tract infection
 Classically four stages:
1. Hypertyhyroid phase – due to release of preformed hormones
2. Euthyroid phase
3. Hypothyroid phase
4. Resolution – return to euthyroid state in 90% patients

54. De Quervain’s Thyroiditis (contd.)
 Clinical features:
 Presents with pain in the neck, fever, malaise
 Firm, irregular enlargement of one or both thyroid lobes
 There may be features of hyper- or hypo-thyroidism
 The condition is self-limiting and, in a few months, the goitre subsides
 There may be a period of months of hypothyroidism before eventual recovery
 10% of patients have acute presentation with severe pain

55. De Quervain’s Thyroiditis (contd.)
 Investigations:
 Raised inflammatory markers
 Absent thyroid antibodies
 Radio-iodine scan shows low uptake
 Treatment:
 Symptomatic treatment given
 Severe cases – glucocorticoids (Prednisone)
 Short-term thyroxine replacement

56. Riedel’s Thyroiditis
 Aka invasive fibrous thyroiditis
 Very rare form
 Thyroid tissue is gradually replaced by fibrous tissue
 Also invades surrounding tissues through the capsule – muscles,
parathyroids, recurrent nerves and carotid sheath
 Probably a collagen disorder and is associated with:
 Mediastinal and retroperitoneal fibrosis
 Periorbital fibrosis
 Sclerosing cholangitis

57. Riedel’s Thyroiditis (contd.)
 Clinical features:
 Painless, hard goitre which is fixed – ‘woody’ thyroid
 Progresses over months to years to produce airway compression
 Features of hypothyroidism and hypoparathyroidism
 Investigations:
 Biopsy required to differentiate from anaplastic carcinoma – generally isthmus is
excised to free the trachea and histo-pathological examination done

58. Riedel’s Thyroiditis (contd.)
 Treatment:
 Excision of isthmus to decompress the trachea
 High-dose corticosteroids
 Thyroxine replacement
 Some patients show response to treatment with tamoxifen (selective estrogen
receptor modulator)

59. Acute Bacterial Thyroiditis
 Aka suppurative thyroiditis
 More common in children
 Often preceeded by upper respiratory tract infection or otitis media
 Bacteriology – Mostly Streptococcus and anaerobes
 Clinical features:
 Neck pain and erythema, fever, dysphagia
 Tender goitre
 Tender, palpable cervical lymphnodes

60. Acute Bacterial Thyroiditis (contd.)
 Investigations:
 Raised WBC count, inflammatory markers
 USG may show localised abscess formation
 FNA and culture-sensitivity testing
 Treatment:
 Antibiotics
 USG guided aspiration/drainage of abscess

61. Thyrotoxicosis

62. Introduction
 Thyrotoxicosis – refers to biochemical and clinical manifestations of
excessive thyroid hormones
 Hyperthyroidism – overproduction of hormones by thyroid gland
 Causes:
1. Diffuse toxic goitre (Grave’s disease) – Primary thyrotoxicosis
2. Toxic multinodular goitre
3. Toxic adenoma – Secondary thyrotoxicosis
4. Rare causes
 Struma ovarii, trophoblastic tumours, metastatic Ca thyroid
5. Exogenous hormone intake – Tertiary thyrotoxicosis

63. Grave’s Disease
 Aka diffuse toxic goitre
 Autoimmune condition with raised thyroid stimulating antibodies
 Syndrome known as Primary Thyrotoxicosis
 Characterized by hyperthyroidism, diffuse goitre and extra-thyroid
conditions
 Ophthalmopathy
 Dermopathy
 Myopathy
 Acropachy

64. Grave’s Disease (contd.)
 Etiopathology:
 Autoantibodies that stimulate TSH receptors on follicular cells
 TSH-Rabs (TRAbs), having longer duration of action, act on follicular cells to
stimulate uncontrolled hormone production
 Also induces hypertrophy and hyperplasia of the gland causing goitre
 Autoantibodies directed against different organs cause extra-thyroid
manifestations

65. Grave’s Disease – Clinical features
 Hyperthyroid symptoms (heat intolerance, excess sweating and thirst,
weight loss)
 Symptoms of adrenergic stimulation (palpitations, fatigue, tremors)
 GIT – Diarrhoea
 CVS – Palpitations, tachycardia, irregular heart rhythm, cutaneous
vasodilation, congestive cardiac failure in elderly
 Musculoskeletal – Fine tremors, muscle wasting
 Genito-urinary system – Oligo- or amenorrhoea, decreased fertility,
miscarriges
 Psychiatry – Irritability, insomnia, nervousness

66. Grave’s Disease – Clinical features
(contd.)
 Ophthalmopathy:
 Exophthalmos – infiltration of retrobulbar tissues with fluid
 Lid retraction – upper eyelid higher than normal (Dalrymple’s sign)
 Lid lag – on downward gaze (von Graefe’s sign)
 Staring look – absence of normal blinking (Stellwag’s sign)
 Absence of forehead wrinkles – Joffroy’s sign
 Lack of convergence – Moebius sign

67. Grave’s Disease – Clinical features
(contd.)
 Dermopathy:
 Pre-tibial myxodema – deposition of myxomatous tissues (hyaluronic acid) in
subcutaneous plane
 Thickened, shiny, red skin with coarse hair in feet and ankles
 Associated with pruritus, palmar erythema, hair thinning
 Acropachy:
 Clubbing of fingers and toes, subperiosteal bone formation and enlarged
metacarpals
 Others:
 Facial flushing, gynaecomastia

68. Grave’s Disease – Management
 Investigations:
 Raised T4 and T3 with suppressed TSH – other tests are not needed if eye signs
are present
 RAIU – diffusely enlarged gland with increased uptake
 Elevated levels of TSH-Rabs
 Treatment:
 Medical – Symptomatic, Antithyroid drugs
 RAIT – Radioactive iodine therapy
 Surgery

69. Grave’s Disease – Medical
management
 Symptomatic:
 Beta blockers – propranolol, nadolol, metoprolol
 Calcium channel blockers – verapamil, dilitiazem
 Oral rehydration
 Antithyroid drugs:
 Drug of choice – methimazole
 Maintained for a prolonged period (6 month-2 years) in the hope that a
permanent remission will occur
 Also given before RAIT or surgery to make patient euthyroid

70. Grave’s Disease – Antithyroid Drugs
 Other drugs:
 Propylthiouracil – DOC in pregnancy, thyroid storm
 Carbimazole – DOC for pre-RAIT/pre-surgery therapy
 Advantages:
 Avoidance of surgery and RAIT
 Disadvantages:
 Prolonged duration of treatment

71. Grave’s Disease – RAIT
 Iodine-131 used – emits beta particles and gamma rays
 Causes complete ablation of thyroid gland
 TSH levels should be high to ensure adequate uptake
 Procedure:
 Patient made euthyroid with anti-thyroid drugs
 Drugs discontinued for 5 days –> 131I given and patient isolated for 7 days
 Takes about 3 months to get full response, therefore antithyroid drugs
continued for 2-3 months
 Eventually patient become hypothyroid and hormone replacement needs to
be continued lifelong

72. Grave’s Disease – RAIT (contd.)
 Contraindication:
 Pregnancy, lactation
 Ophthalmopathy
 Advantages:
 No surgery and no prolonged drug
therapy
 Disadvantages:
 Ophthalmology gets aggravated
 May cause hypoparathyroidism

73. Grave’s Disease – Surgery
 Cures by reducing the thyroid below a critical mass
 Options:
 Sub-total thyroidectomy – 4-7 g remnant thyroid; patient becomes euthyroid
but risk of recurrence
 Total thyroidectomy – No risk of recurrence but lifelong thyroxine replacement
 Lobectomy – In case of toxic nodules
 Patient needs to be made euthyroid pre-operatively

74. Grave’s Disease – Surgery (contd.)
 Indications:
 When RAIT contraindicated
 Large goitre with compression
 Suspected carcinoma
 Rapid control required
 Disadvantages:
 Recurrence in case of sub-total
thyroidectomy
 Risk of injury to nerves and parathyroids
 Advantages:
 Rapid cure
 High success rate
 Relieves ophthalmopathy

75. Secondary Thyrotoxicosis
Primary Thyrotoxicosis
1. Symptoms first –> swelling
2. Autoimmune etiology
3. Features of thyrotoxicosis are marked
4. Ophthalmopathy is common
5. Younger age group
Secondary Thyrotoxicosis
1. Occurs in pre-existing swelling
2. Risk factors include iodine deficiency,
dietary goiterogens, hereditary factors
3. Less severe and slowly progressive
4. Cardiac signs are common
5. Elderly

76. Simple (non-
toxic) Goitre

77. Diffuse Simple Goitre
 Develop as a result of stimulation of the thyroid gland by TSH
 Iodine deficiency – in response to a chronically low level of circulating thyroid
 Pituitary adenoma – inappropriate secretion from a microadenoma in the
anterior pituitary (which is rare)

78. Thank you.