Goitre (Including Multi-nodular)

DEFINITION
Non-toxic goitres
Enlargement of a thyroid gland containing follicles that are functionally altered.

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INCIDENCE

Incidence

Common.

Age

Often later-developing lesions.

Gender

F>M.

Geographical distribution

Goitres are endemic in areas of iodine deficiency.
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AETIOLOGY

Multifactorial

Sieve

Familial defects including 'dyshormonogenesis' (genetic defects in correct synthesis of thyroid hormones)
Enzyme deficits (eg defects impairing iodine incorporation).
Endemic goitre (iodine deficiency).
Goitrogens, eg in cabbage and cassava root (suppress T3 and T4).
Certain drugs, eg lithium (suppress T3 and T4).
Much sporadic goitre is of unknown cause.

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BIOLOGICAL BEHAVIOUR


Pathology
Under persistant low grade stimulation
Get differential growth and involution, leading to an irregular nodularity.
Resulting tissue tensions generate small haemorrhages and follicle ruptures
Ultimately leads to a fibrotic cystic and disorganised gland.
May be followed by functional autonomy

Pathophysiology
Symptoms relate to cosmesis, mass effect and thyroid function.
Thyroid function:
If the underlying cause is severe, gland hypertrophy is inadequate to supply hormone to peripheral tissues, allowing goitrous hypothyroidism (eg severe iodine deficiency).
TSH increases, though usually unhelpfully.
MNG may also become toxic (see Toxic MNG).

Complications

Endocrine abnormalities
Sudden haemorrhage into a nodule, with swelling, and compression possible.
May mask a developing neoplasm.
- rate of cancer in an MNG is same as any nodule (~5%)
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MANIFESTATIONS

Symptoms


Local

Cosmetic complaint.
Mass effect
Stridor, SOB (trachea).
Hoarseness (laryngeal nerves - rare in simple goitre).
- can rarely result from pressure on nerves due to haemorrhage into the gland
Dysphagia (oesophagus).
Headache (venous outflow).

Endocrine

Hypothyroidism if severe underlying cause.
Toxic MNG - see card.
Jod-Basedow phenomenon with iodine consumption.

Signs


Refer also hypo/hyperthyroidism cards.

Observe

Above features - NB mass moves up with swallow.
Pemberton's sign.

Palpate

Enlarged gland, moves up with swallow.
- diffuse vs nodular?
- nodules may be individually palpable.
Tracheal deviation?
Thrill possible.

Percuss

Sternum - ?retrosternal extension.

Auscultate

Bruit possible.
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INVESTIGATIONS

Biochemistry

TSH single best test
Additionally T4, T3 as reqd
Nodule
Work up as for any thyroid nodule
Work up any nodule within an NMG with concerning imaging features (hypoechogenicity, hypervascularity, microcalcifications).

Immunology
Antimicrosomial or antithyroglobulin antibodies turn diagnosis in favour of Hashimoto's.

Imaging

Ultrasound +/- FNA as above
CT/MRI if concern for retrosternal extension.
RAIU (radioactive iodine uptake) may be useful in toxic picture

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MANAGEMENT

Indications for Treatment
1. Discomfort
2. Mechanical obstruction
3. Subclinical or overt thyrotoxicosis
4. Suspicion for cancer
5. Cosmesis (uncommonly an isolated presenting complaint)
6. Retrosternal

Conservative

Stop goitrogens if known cause.

Medical

1. Thyroxine-suppressing therapy?
Evidence lacking from several prospective trials
- side effects (bone mineral loss and cardiotoxicity) negate any advantage.
2. Radio-iodine?
Effective with 40-60% shrinkage in most within 2 years
Can decrease compressive symptoms
Complications:
- radiation induced thyroiditis or hypothyroidism (~20%+)
- malignancy (very rare)
?Recombinant TSH to augment radioiodine uptake
- recent studies into this.

Surgical

Mainstay of treatment.
Complication rates are low (<2%) in experienced centers
- and with meticulous hemostasis and liberal parathyroid autotransplantation
One of the most critical aspects is safe securing of airway
- conscious fiberoptic intubation if marked deviation or compression.
Rarely need to go into chest given cervical origin and arterial anatomy
Thyroid replacement for life - 1.7ug/kg usual dose.

Notes on MNG Surgery
1. Generous collar incision
- wide subplatysmal flaps, separating flaps in midline
- divide sternothyroid muscle near upper pole for exposure
2. Open plane between larynx and upper pole
- expose superior thyroid artery, vein, and external branch of superior laryngeal nerve.
- (can use nerve stimulation to trace out path during ligation of upper pole vessels)
3. Individually ligate superior thyroid artery and vein on capsule; minimizing risk to nerve
4. With upper pole mobilized, partially rotate gland up and out
- exposing middle thyroid vein, ligated in continuity
5. Enter correct fascial plan with gentle finger dissection.
- goitre can be delivered into wound, even if partially substernal
6. Identify RLN and parathyroids
- inferior thyroid vessels taken off.
7. RLN taken back to insertion
- terminal branches of inferior thyroid artery are divided and ligated between ligaclips
- RLN and parathyroids gently separated from thyroid and ligament of Berry and divided, freeing lobe and isthmus.
- prominent lobe of Zuckerkandl can make dissection more difficult at this time.
8. Devascularized parathyroids:
- autonomous transplant into SCM, mark site with permanent suture
- if unsure, nick capsule with iris scissors or 11 blade --> if bleeding and normal colour return then safe to leave it.
9. Closed suction drain to obliterate dead space,
10. Layered closure.

Subtotal?
Sometimes done if wanting to preserve at least one superior parathyroid when unsure

Post-op Care
Drain out d1
Calcium supplementation based on symptoms, serum calcium and phosphorus and serum parathyroid
Thyroid hormone replacement prior to dismissal
- recheck TFTs in 6 weeks.

Pitfalls.
1. Posteriorly displaced goitres
- nerve may run over gland between nodules
- risk should be evident by posterior displacement on scan (e.g. retroesophageal)
--> find nerve on upper pole, where pierces inferior constrictor, then follow back proximally
--> may need to remove posterior portion piecemeal so don't put tension on RLN
[with anteriorly displaced goitres, the RLN and parathyroid are often diplaced posteriorly, safely out the way]



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