THYROID DISEASESTHYROID DISEASES

Anatomy of Thyroid Gland

Arterial supply• Sup. thyroid artery

(branch of ext carotid artery)

• Inf. thyroid artery (branch of thyrocervical trunk)

• Thyroidea ima (from brachiocephalic artery/arch of aorta)

Anatomy of Thyroid Gland

Venous drainage• Sup. Thyroid (drains into

internal jugular vein)

• Middle thyroid (drains into internal jugular vein)

• Inf. thyroid (drain into left brachiocephalic vein)

Ectopic Thyroid & Anomalies

Lingual

Median ectopic thyroid

Lateral aberrant thyroid

Intrathoracic aberrant thyroid

Pyramidal lobe

Ectopic Thyroid & Anomalies

• Lingual thyroid– Rounded swelling at

back of tongue– May cause dysphagia,

impairment of speech, resp obstruction, hemorrhage

• Median ectopic thyroid– Upper part of the neck– Mistaken for

thyroglossal cyst

• Lat aberrant thyroid– ‘normal’ thyroid

laterally must be considered & treated as mets in cervical LN from occult papillary thyroid ca

Ectopic Thyroid & Anomalies

• Thyroglossal cyst– Any part of thyroglossal

tract– Midline– Move upward on protrusion

of tongue– >1cm, excised because

prone for infection– Infected cyst often mistaken

for abcess & incised thyroglossal fistula

Ectopic Thyroid & Anomalies

• Thyroglossal fistula– Infection/inadequate

removal of throglossal cyst

– Cutaneous opening drawn upward on protussion of tounge

– Discharge mucus recurrent attack of inflammation

Classification of Thyroid Swelling

• Simple goiter (euthyroid)– Diffuse hyperplastic

• Physiological

– Multinodular

• Toxic– Diffuse : Grave’s disease– Multinodular– Toxic adenoma

• Neoplastic– Benign – Malignant

• Inflammatory– Autoimmune

• Hashimoto’s ds

• Chronic lymphocytis thyroiditis

– Granulomatous• De Quervain’s thyroiditis

– Fibrosing• Riedel’s thyroiditis

– Infective• Acute (bacterial & viral

thyroiditis)

• Chronic (TB, syphilis)

– Other • amyloid

Simple Goiter

• Aetiology– Iodine deficiency– Dyshormogenesis– Goitrogens

• The natural history of simple goiter– Persistent growth stimulation causes diffuse hyperplasia– Mixed patterns develops with areas of active and inactive

lobules as result of fluctuating stimulation– Active lobules become more vascular and hyperplastic until

haemorrhage occurs, causing central necrosis– Necrotic lobules coalesce to form nodules filled with either

iodine-free colloid or a mass of new but inactive follicles– Continual repetition of these processes result in a nodular goitre

Diffuse Hyperplastic Goiter

• Correspond to the 1st stages of natural history

• Childhood (endemic areas), puberty, pregnancy

• soft, diffuse and may become large enough to cause discomfort.

Nodular Goiter

• Later stage of natural history of simple goitre

• Multiple multinodular goitre• may be colloid or cellular• cystic degeneration and

haemorrhage is common• Can develop retrosternal goitre

– dyspnea, cough, stridor, SVC obstuction

Solitary Nodule

• 70% are clinically isolated, 30% dominant

• May have risk of neoplasia

• 15% isolated - malignant• 30-40% - follicular

adenomas• Remainders – non

neoplastic, colloid degeneration, thyroiditis, cysts

• Ix – TFT– autoAb titres– Isotope scan

• Hot/cold

• 80% cold & only 15% malignant

– U/s : solid/cyst– FNAC

Hypothyroidism

Autoimmune thyroiditis (Hashimoto’s ds, 1o

myxodema)Iatrogenic

DyshormongenesisGoitrogens

2o to pituitary or hypothalamic diseaseEndemic cretinism

Signs & Symptoms

Hashimoto’s disease

• destruction of thyroid cells by various cell- and Ab-mediated immune processes.

• Ab bind and blocking the TSH inadequate thyroid hormone production and secretion

• Middle age woman• Uniformly enlarge & firm (occ

asymmetrical & irregular)• Thyroglobulin & microsomal Ab (90%)

Hashimoto’s disease

• TFT– Low T4 & T3– High TSH

• Treatment– levothyroxine sodium, usually for life.– goal of therapy is to restore a clinically and

biochemically euthyroid state.– standard dose is 1.6-1.8 mcg/kg lean body weight per

day

Hyperthyroidism

Diffuse toxic goitre (Graves’ disease)Toxic nodular goitre

Acute thyroiditisGestational thyrotoxicosis

Exogenous iodineDrugs- amiodarone

Thyrotoxicosis factitiaTSH-secreting pituitary tumours

Metastatic differentiated thyroid carcinomaHcg-producing tumours

Hyperfunctioning ovarian teratomathyrotoxicosis factitia (rare)

1o vs 2o hyperthyroidism

1o (Grave’s ds) 2o

Enlargement of thyroid and toxic features appear simultaneously

Goitre appears first, toxic features develope after an interval

Toxic features are usually severe Toxic features are mild

Nervous manifestations Cvs manifestations

young elderly

Exopthalmos and eye signs are common

These are absent

small, diffuse, smooth large, nodular, irregular

Signs & symptoms

• Symptoms– Tiredness– Emotional liability– Heat intolerance– LOW– Excessive appetite– Palpitations– Myopathy – Oligomenorrhea

• Signs – Tachycardia– Hot, moist palms– Eye sign

• Exopthalmos• Lid lag/ retraction• Dilated pupils• Double vission

– Agitation– Thyroid goitre and

bruit– Fine tremor

Exophtalmos

Pretibial myxoedema

Diffuse Toxic Goiter (Grave’s ds)

• autoimmune disease

• Abnormal TSH-Ab bind to TSH prolonged effect increase hormon

• Young women

• No preceding history of goiter

• Smoothy enlarged

• Eye signs

Toxic Nodular Goiter (2o)

• Simple goiter present b4 hyperthyroidism

• Middle aged/elderly

• Many cases, nodule inactive but intranodular tissue is active

• Nodule activated hyperthyroidism

Investigations

• Essential– Serum TSH (T3 and T4 if abnormal)– Serum thyroid autoantibodies– FNAC of all palpable discrete swellings

• Optional– Calcium and albumin– CXR and thoracic inlet if tracheal

deviation/retrosternal – Isotope scan if discrete swelling and toxicity coexist

Thyroid funtional

state

TSH

(0.3 – 3.3µU -1)

Free T4

(10 – 30 nmol-1)

Free T3

(3.5 – 7.5 µmol-1)

Euthyroid Normal Normal Normal

Thyrotoxic Undetectable High High

Myxoedema High Low Low

Suppressive T4 therapy

Undetectable High High

T3 toxicity Low/Undetectable Normal High

Treatment of thyrotoxicosis

• Antithyroid drugs – carbimazole

• ß-adrenergic blocking drugs

• Anti-thyroid drugs combined with subsequent thyroidectomy

• Radioactive iodine-131

Anti-thyroid Drugs

• restore in euthyroid state and maintain for prolong period in hope of remission

• Carbimazole – 10mg 8-hourly– Continue for 12 months– Aware of toxic symptoms within 2 weeks, if symptoms

recur further 6 months treatment with surgery is advised

– High relapse rate (60%) after terminating the treatment (even in 2 or more years of tx)

• Medical tx alone usually confined to 1° hyperthyroidism in children and adolescents

• Side effects of carbimazole:- Drug rash - Fever- Arthropathy- Lymphadenopathy- Agranulocytosis (sore throat)

ß-adrenergic blocking drugs

• Propanolol induces rapid symptomatic improvement of cvs features in patients with severe hyperthyroidism

Surgery for thyrotoxicosis

• Preoperative preparation– Anti-thyroid drugs– ß-adrenergic blocking drugs (alternative)

• Extent of resection– size of gland– age of patient– experience of surgeon– need to minimise risk of recurrent toxicity

• Hemithyroidectomy, total thyroidectomy (depends)

• It cures by reducing mass of overactive tissue in diffuse toxic goitre and toxic nodular goitre

• Advantages: the goitre removed, cure is rapid and cure rate high if surgery adequate

• Disadvantages: recurrence in 5% of cases and risk of surgery complications

Procedures

The thyroid gland is removed.Either one lobe of the thyroid gland,or the entire gland, is removed,depending on the disease processbeing treated

While the patient is deep asleep and pain-free (general anesthesia), an incision is made in the front of the neck.

Complications of thyroidectomy• Hormonal disturbances

– Tetany (parathyroid)– Thyroid crisis – Hypothyroidism (due to extensive removal of thyroid tissue)– Late recurrence of hyperthyroidism (d2 inadequate operation in

toxic gland)

• Damage to related anatomical structures– Recurrent laryngeal nerve– Injury to trachea– Pneumothorax

• Complications of any operation– Haemorrhage– Sepsis– Postoperative chest infection– Hypertrophic scarring (keloid)

Radioactive Iodine

• destroys thyroid cells• reduces the mass of functioning thyroid tissue to below a

critical level• Swallow a glass of water containing radioiodine• Useful in recurrence of hyperthyroidism after

thyroidectomy (takes 2-3 months)• high incidence of late hypothyroidism (75-80%) after 10

years• Contraindicated in pregnant women (affecting infant’s

thyroid) • No evidence therapeutic radioiodine is carcinogenic or

teratogenic

Neoplasms

Classification

benign malignFollicular adenoma

1o

2o

Follicular epit – diff

• papillary (60%)

• follicular (20%)

Follicular epit – undiff

• anaplastic (10%)

Parafollicular cells

• medullary (5%)

Lymphoid cells

• lymphoma (5%)

Mets – local infiltrate

Benign Follicular Adenoma

• Clinically, solitary nodules

• F:M = 4:1

• HPE to differentiate adenoma and carcinoma (in adenoma there is no invasion of capsule or of pericapsular blood vessels)

• Tx: wide excision (lobectomy)

Thyroid carcinoma

• F:M = 3:1 (incidence 3.7 in 100 000)• Arising in pre-existing goitres• Reported following radiation of the neck in

childhood• Clinical features

– Goiter– LN (papillary ca)– recurrent laryngeal nerve paralysis (locally

advanced dis.)– usually euthyroid

• Anaplastic – hard, irregular, infiltrating

Papillary carcinoma• Commonest (60%)• Young adults, adolescents or children• Slow growing tumour• Spread

– lymphatic (late and common)– Blood-born (uncommon)

• Occult carcinoma- enlarged lymph node in the jugular chain with no palpable abnormality of thyroid (good prognosis)

• Tx– combination of surgery (total lobectomy or

thyroidectomy), thyroid suppression by T4 and radioiodine

numerous papillae having a fibrovascular stalk covered by a single to multiple layers of cuboidal epithelial cells

Follicular carcinoma

• Young and middle-aged adults

• Common in area of endemic goiter

• Spreads– Blood stream (common)

• worsen the prognosis• mortality rate twice fr papillary ca

– Lymphatic rare

• Tx: same as papillary ca

Invasion of capsule and the vascular spaces in the capsular region in follicular carcinoma.

Papillary vs. Follicular ca

Papillary (%) Follicular (%)

Male incidence 22 35

LN mets 35 13

Blood vessel invasion 40 60

Recurrence 19 29

Mortality rate 11 24

Distant mets 45 75

Nodal mets 34 12

Prognosis : PAPILLARY > follicular

Medullary carcinoma

• Arises from parafollicular C cells • may secrete calcitonin (tumour marker)• any age• F = M• associated with other cancers in MEN syndrome (type II)• Deposits of amyloid between the nests of tumour cells• Lymph node and blood-borne involvement are common• Tx: total thyroidectomy and lymph node clearance (if

involved)

Characteristic ‘cell balls’ and amyloid in medullary carcinoma

Anaplastic carcinoma

• elderly• Rapid local spread takes place with compression

and invasion of the trachea• Early dissemination to the regional lymphatics

and blood-stream spread to the lung, skeleton and brain

• Tx– radical thyroidectomy – palliative radiotherapy – temporary relieve

(tracheostomy for obstructed airway)

TNM stagingPrimary tumor (T)

TX: Primary tumor cannot be assessed T0: No evidence of primary tumor T1: Tumor 1 cm or less in greatest dimension limited to the thyroid T2: Tumor more than 1 cm but not more than 4 cm in greatest dimension limited to the thyroid T3: Tumor more than 4 cm in greatest dimension limited to the thyroid T4: Tumor of any size extending beyond the thyroid capsule

Regional lymph nodes (N) NX: Regional lymph nodes cannot be assessed N0: No regional lymph node metastasis N1: Regional lymph node metastasis

– N1a: Metastasis in ipsilateral cervical lymph node(s) – N1b: Metastasis in bilateral, midline, or contralateral cervical or mediastinal lymph node(s)

Distant metastases (M) MX: Distant metastasis cannot be assessed M0: No distant metastasis M1: Distant metastasis

Prognosis

• Well differentiated tumours– Long survival even with presence of LN

deposits

• Anaplastic tumours– Pt dead within a year (due to local invasion or

widespread dissemination)

Thyroiditis

Chronic lymphocytic (autoimmune) thyroiditis

• Raised titer of thyroid Ab• Family history of autoimmune disease• goitre (diffuse or nodular) with characteristic ‘bosselated’

feel• Common in menopause women• any age• mild hyperthyroidism initially and later hypothyroidism • Dx: raised serum level of thyroid antibodies, FNAC,

biochemical test of thyroid fx if hypothyroidism is present• Tx: replacement with thyroxine (hypothyroidism),

thyroidectomy maybe necessary if goitre is large

Granulomatous thyroiditis• subacute thyroiditis, de Quervain’s thyroiditis• virus infection• Features

– pain in the neck– Fever– Malaise– firm, irregular enlargement of one or both thyroid lobes– Raised ESR– absent thyroid antibodies– serum T4 is high or slightly raised– radioiodine uptake of gland is low– Self limiting, goitre subsides in few months

• Dx - confirmed by FNAC & radioactive iodine uptake - rapid symptomatic response to prednisolone in acute case of

severe pain

Riedel’s thyroiditis

• Rare• slightly enlarged but is woody hard with

infiltration of adjacent tissues• represent late stage of Hashimoto’s disease or

inflammatory origin• Mistaken for thyroid ca (histologically gland is replaced by

fibrous tissue containing chronic inflammatory cells)

• a/w other conditions such as retroperitoneal fibrosis, sclerosing cholangitis, and fibrosing mediastinitis

• Wedge resection of portion of gland if tracheal compression symptoms develop