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

HypothalamusTRH PituitaryTSH Thyroid GlandThyroid hormone T4

Thyroid Gland95% 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 Hypothyroidism Prognosis 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 obesitydelayed reflexes dry skinpuberty gen delay Increased body hair Pallor Vitiligo Proximal muscle weakness

Hypothyroidism in Older children – Diagnosis and treatment FT4 TSH TPO Thyroxine 100ųg/m 2 /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 TransientMother high TSI PersistentFamily 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