Thyroiditis


DEFINITION

1. Hashimotos (Chronic Lymphocytic)
2. De Quervain (Subacute Granulomatous)
3. Subacute Lymphocytic
4. Acute Suppurative
5. Reidel Struma
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INCIDENCE

Hashimoto
Most common thyroiditis
Most common cause of hypothyroidism in iodine-sufficient areas.
- prevalence is increasing.
F>M 20:1
Age 45-65
Genetic predisposition; inheritable trait

Associated diseases

Pernicious anaemia.
Sjogren's syndrome.
Chronic active hepatitis.
SLE
Rheumatoid arthritis.
Adrenal insufficiency.
Diabetes mellitus.
Grave's disease.

De Quervain
Most common cause of a painful gland.
F>M 3:1
Us. 30-50 yr

Subacute Lymphocytic
30-50% of thyroiditis
Mainly women in 40s-50s
Post-partum form; 1/3 develop chronic

Acute Suppurative
Rare; 2/3s with pre-existing thyroid problem.

Reidel's
mean 50yrs, 80% female

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AETIOLOGY

Hashimoto
Autoimmune.

De Quervain
Likely viral; us. preceded by an URTi
- many possible agents implicated including mumps, EBV

Subacute Lymphocytic
Autoimmune.
Antimicrosomial antibodies present in 50-80%

Acute Suppurative
Infective; us. bacterial,  also fungal or parasitic

Reidel's
Invasive fibrous thyroiditis

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BIOLOGICAL BEHAVIOUR

Hashimoto

Pathogenesis
Chronic inflammatory disease.
Lymphocytic infiltration of the gland.
- T-cells probably primary defect: recognise processed thyroid antigens in association with specific MHC antigens.
- activated helper T cells induce B cell secretion and may activate cytotoxic CD8+ cells
--> serum antibodies found against several components of thyroid tissue including thyroglobulin, peroxidase, TSH receptor, iodine transporter.
- antibodies may fix complement augmenting thyroid cell killing, or induce Fas-Fas apoptosis.
Thyroid follicles are histologically small, with Hurthle cells and fibrosis
- may be small and atrophic due to widespread fibrosis.

Natural history
Goitre and thyroid dysfunction is the usual presentation.
Thyroid parenchyma is replaced by lymphocytes or fibrous tissue.
Subclinical thyroid failure with compensatory rise in TSH.
Initially T4 declines, but T3 remains normal.
Eventually, T3 levels drop -> frank hypothyroidism.

Hashitoxicosis
Occasionally early in the disorder inflammation may be severe enough to disrupt follicles.
- so present first with transient hyperthyroidism.

Complications
Increased risk of developing B cell (non-Hodgkin) lymphomas.
- these us. limited to gland

Subacute Lymphocytic
If post-partum, us. within 3 months from delivery
Can progress to hypothyroidism may be persistent

Acute Suppurative
Gland highly resistant to infection; rich blood and lymph, protective fascia.
90% have a pyriform sinus

Reidel's
Stone-hard mass. symptoms vary.
Can get obstructive symptoms and voice changes as gland enlarges.
Hypothyroidism in one third, also possibly hypoparathyroidism.
Antithyroid antibodies in half.
Can be confused with cancer - FNA or biopsy
- FNA shows fibrosis, lymphocytes and plasma cells.
Self limiting except for possible compressive symptoms requiring surgery.
Steroids may be beneficial in some.
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MANIFESTATIONS

Symptoms
Hashimoto
Fullness or discomfort around neck
Hypothyroidism in only 20% at diagnosis
- then increases by 5% per year
- few get hyperthyroidism (5%)

De Quervain
Constant, starts in one lobe, extends bilaterally
Fever common.
Can last months, with hyperthyroid symptoms developing in 70%.
- can be followed by euthyroidism or hypothyroidism (20-30%; persistent in only 5%)

Subacute Lymphocytic
Thyroid tenderness and pain unusual.
Usually present with hyperthyroidism.

Acute Suppurative
Neck pain, fever
Compressive symptoms with pharyngitis, dysphagia
Fluctuant mass possible

Signs
Hashimoto

Diffuse goitre
- may or may not be symmetrical.
- firm, irregulary, nontender
- may have single large nodules occasionally mistaken for tumours.
General outline of the gland is preserved.
- charicteristically having an enlarged pyramidal lobe
Rubber consistency
May have cervical lymphadenopathy
Features of hypothyroidism
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INVESTIGATIONS

Hashimoto

Hormones
TSH elevated.
- T4, then T3 deficiency.
Immunology
Elevated antibodies to thyroid-specific antigens
Antithyroglobulin antibody
Antithyroid peroxidase (anti-TPO) (>200 IU/ml strongly suggestive)
Antithyroid microsomal antibodies (>1:6,400 strongly suggestive)
- these are low in other thyroid diseases
Biopsy
Needle biopsy shows lymphocytic infiltrate.
RAIU
Can be increased, decreased or normal depending on extent of follicle destruction
USS
Diffusely enlarged gland,
Dominant nodule?
Investigate as for any nodule.

De Quervain
Elevated ESR, decreased RAIU, elevated serum thyroglobulin and thyroid hormones (T4 disproportionately up).
Normal ESR or normal thyroblobulin rule out diagnosis
Thyroid antibody titers elevated in 10-20%, become negative 1-6m after recovery.
Biopsy rarely needed

Subacute Lymphocytic
Thyroid hormones elevated T4>T3
Thyroglobulin aelevated in actue form
Serum TSU down; RAIU decreased (unlike Graves).

Acute Suppurative
TFTs are normal, RAIU generally normal or cold if abscess.
Imaging shows extent
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MANAGEMENT

Hypothyroidism
Thyroxine replacement (T4) therapy.
- may also be indicated if TSH in normal range but wanting to prevent progression to overt hypothyroidism in the at-risk

Hashimoto's
Role of surgeon is to confirm diagnosis and address any nodules.
Enlarging or persistent goitre or suspect nodules will lead to surgery.

De Quervain
Therapy for hyperthyroidism rarely needed as pre-formed T4 being released.
B-blockers may help control symptoms
Most treatment = pain control; NSAIDs
Tapering steroids may be reqd

Subacute Lymphocytic
Beta-blockers for Sx
Propranolol in lactating females.
If hypothyroid phase lasts >6m, permanent hypothyroidism is likely.

Acute Suppurative
Antibiotics, surgical drainage, possibly lobectomy.
Need to cover staph, strep, but go broad spectrum if no organism yet identified


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