Thyroid Disease

Embryology

• TG develops from floor of Pharynx at 4 weeks

• travels inferiorly

• thyroglossal tract disappears - cystic elements may remain as thyroglossal cyst

• Diverticulum becomes bi-lobed & fuses with ventral aspect of 4th pharyngeal pouch

• Organogenesis under genetic control - transcription factors TTF1, TTF2, Pax8 crucial

• Hypothalamus TRH

• Pituitary TSH

• Thyroid Gland Thyroid hormone T4

• Thyroid Gland 95% T4

5% T3

• T4 deiodinated peripherally to T3

and rT3

Circulating Thyroid Hormones

• 99.5% protein bound

• 0.5% free and active

• Exert negative feedback to hypothalamus and Pituitary

Thyroid Gland

Controlled by TSH

1. Iodide

2. Iodide Iodine

3.Iodine + tyrosine mono and diiodotyronine

4. Coupling T3 and T4

5. Proteolytic enzyme T4 and T3

Action of Thyroid Hormones

1.Speed up metabolism

2.Essential for: growth

mental development

3.Increased sensitivity of CNS and CVS to catecholamines

Disorders

Hypothyrodism

Hyperthyroidism

Congenital

Acquired

Congenital Hypothyroidism

Incidence in Europe

1 in 3,500

Illingworth, 1983

Causes of Congenital Hypothyroidism

1. Dysgenesis (85%)

2.Ectopic

3. Enzyme defect (10%)

4. Pituitary, Hypothalamic

5. Iodine deficiency

Congenital Hypothyroidism - Symptoms

• Sleepiness

• Poor Feeding

• Prolonged jaundice

• Constipation

• Hoarse cry

• FHx congenital hypothyroidism

• Maternal history of thyroid disease

Congenital Hypothyroidism - Signs

• Jaundice

• Cold

• Large Tongue

• Coarse facies

• Large fontanelles

• Hypotonia

• Distended abdomen

• Umbilical hernia

• Slow reflexes

Congenital Hypothyroidism Diagnosis

• TSH

• T4 (low or normal)

• Xray knee

• Technetium scan

Treatment

• L-Thyroxine

• Excess - craniosynostosis

Congenital HypothyroidismPrognosis

1.Early treatment - screening programme

2.Social class

Hypothyroidism in Older children

1. Congenital

2. Autoimmune thyroiditis

Hashimoto’s thyroiditis

Associated with other conditions

eg DM, Addisons,Trisomy 21, TS,

3. Post radiation

4. Pituitary, Hypothalamic (TSH level low for FT4)

5. Sick euthyroid syndrome

Hypothyroidism in Older children - symptoms

• Weight gain

• tiredness

• constipation

• cold intolerance

• slowing of growth +/- short stature

• ? poor school performance

• Delayed puberty (occ precocious), irregular periods

• History of SUFE, other AI disease

• Family history

Hypothyroidism in Older children - signs

• Myxoedatous facies

• short stature

• goitre

• obesity delayed reflexes

• dry skin puberty gen delay

• Increased body hair

• Pallor

• Vitiligo

• Proximal muscle weakness

Hypothyroidism in Older children – Diagnosis and

treatment

• FT4 TSH

• TPO

• Thyroxine 100ųg/m2/day

(gradually reach dose)

• ? Other AI disease

• some remit spontaneously

Normal Thyroid Gland

• Not visible

• Barely palpable

Matovinovic, JAMA 1961

Simple or Colloid Goitre

• Clinically euthyroid

• TSH

• T4 normal

• Thyroid antibodies

Neonatal Hyperthyroidism

• Transient Mother high TSI

• Persistent Family History of Graves

Hyperthyroidism - Symptoms

1.CNS - nervous, behaviour, poor school performance

2. GIT - appetite, weight loss, diarrhoea

3. Heat intolerance

TSH suppressed and peferential conversion T4-T3 measure T3

Hyperthyroidism - Signs

1.Eyes

2.Tachycardia

3. Tremor

4. Brisk tendon reflexes

5. Increased growth and bone age

Investigations

• FT4, FT3, TSH

• TPO

• TRAB

• Ultrasound

• Technetium Scan

• +/- TRH Test

Treatment of Thyrotoxicosis

Carbimazole

Side effects: rash

arthralgia, SLE

neutropenia

2 year course; 50% remission

Radioactive Iodine

Surgery