Thyroid Disorders In Children

Thyroid gland Location: Located close to thyroid cartilage. Has two lateral lobes connected by thyroid isthmus medially. Development: first endocrine gland to appear during development. Develops from endodermal floor of early pharynx

Thyroid gland • Thyroid gland is composed of over a million cluster of follicles • Follicles are spherical & consists of epithelial cells surrounding a central mass (colloid) • Thyroglobulin is a storage room • Two main hormones: – Tetraiodothyronine (Thyroxin) = T4 – Triiodothyronine = T3

Production of Thyroid Hormones NIS (Na+/I- Sympoter) TPO

t1/2 = 5-7d t1/2 = < 24 hrs

Normal Daily Thyroid Secretion Rate: T4 = 100 ug/day T3 = 6 ug/day ( ratio T4:T3 = 14:1 ) T4 Protein binding + 0.03% free T4 85% (peripheral conversion) T3 Protein binding + 0.3% free T3 15% (10-20x less than T4)

Effects of thyroid hormones Foetal brain & skeletal maturation • Increase in basal metabolic rate • Inotropic & chronotropic effects on heart • Increases sensitivity to catecholamines • Stimulates gut motility • Increase bone turnover • Increase in serum glucose Decrease in serum cholesterol • Conversion of carotene to vitamin A • Play role in thermal regulation

Thyroid disorders: Aetiology • Congenital • Acquired – Primary – Secondary – Tertiary

Congenital hypothyroidism Agenesis (No goiter) or dysgenesis (aplasia, hypoplasia, ectopic gland) are the commonest causes…..85% Dyshormonogenesis (10%) and a goiter will be present. Pendred syndrome with sensorineural deafness is the commonest (often euthyroid). Transplacental maternal TSH receptor blocking Abs (TRBAb) account for 5% of cases. Pituitary failure and maternal ingestion of goitrogens are other causes

One of the most common treatable causes of Mental retardation CH Screening is the most cost effective program Almost all affected Newborns have no S/S at birth Congenital Anomalies increased by 10% (cardiac) It is permanent in more than 90% of the cases The earlier diagnosis the better IQ

A. Delayed epiphyseal appearance B. epiphyseal dysgensis

Signs of congenital hypothyroidism • 31% prolonged jaundice • 23% umbilical hernia • 21% constipation • 21% macroglossia • 19% feeding problems • 16% hypotonia • 16% hoarse cry • 13% large posterior fontanelle • 10% dry skin • 5% hypothermia • 2% goiter • 40% delayed bone age

Neonatal screening for congenital hypothyroidism • Routine in most countries worldwide • Filter paper blood spot measuring TSH • Why ?? • Clinical manifestations at birth, usually are subtle or even absent (passive transplacental maternal thyroxin) • At birth, surge of TSH (stress of delivery) up to 30 -40 µu/ml • Early detection will prevent mental retardation or decreasing IQ of affected neonates • Thyroxin is important for CNS development from birth till 3 years of life • Screening program will miss 2ry/tertiary cases • The program is hampered by a high rate of false positive results

Management of congenital hypothyroidism • Documentation – Free T4, TSH • Thyroid scan, ultrasound (optional) • Treatment (normal size full term) – start L-thyroxin at 10-15 mcg/Kg daily – Monitor TSH every 2-3 months during first 2 years of life.

Acquired hypothyroidism • More common than hyperthyroidism • 99% is primary (< 1% due to TSH deficiency) • Hashimoto’s – most common thyroid problem (4% of population) – most common cause in iodine-replete areas – chronic lymphocytic thyroiditis – Associated with TPO antibodies (90%), less commonly Tg antibodies • Iatrogenic Hypothyroidism from radioactive iodine therapy

Symptoms Symptoms – General Slowing Down – Lethargy/somnolence – Depression – Modest Weight Gain – Cold Intolerance – Hoarseness – Dry skin – Constipation (↓ peristaltic activity) – General Aches/Pains – Arthralgias or myalgias (worsened by cold temps) – Brittle Hair – Menstrual irregularities – Excessive bleeding – Failure of ovulation – ↓ Libido

Examination • Dry, pale, course skin with yellowish tinge • Periorbital edema • Puffy face and extremities • Sinus Bradycardia • Diastolic HTN • ↓ Body temperature • Delayed relaxation of reflexes • Megacolon (↓ peristaltic activity) • Pericardial/ pleural effusions • Congestive heart failure • Non-pitting edema • Hoarse voice • Myopathy

Diagnosis Congenital hypothyroidism • Thyroid hormone level • TSH • Thyroid scan Maternal investigations: TFT and Abs Acquired Hypothyroidism • fT4 • Thyroid antibodies • Thyroid ultrasound • TSH: low in secondary hypothyroidism -high in primary hypothyroidism • TRH test: to differentiate between secondary & Tertiary hypothyroidism

Hyperthyroidism(Thyrotoxicosis) Definition • Excessive secretion of T3 & T4 • Affects metabolic processes in all body organs • Hyperthyroidism is 4-10 times more prevalent in women

Graves’ Disease Most common cause of hyperthyroidism Goiter, proptosis TSH-R antibody (stimulating) = TRAB 40-70% relapse after 2 years of treatment

Hyperthyroidism S&S Heat intolerance Hyperactivity, irritability Weight loss (normal to increased appetite) Diarrhea Tremor, Palpitations Diaphoresis (sweating) Lid retraction & Lid Lag (thyroid stare) Proptosis Menstrual irregularity Goiter Tachycardia

A 15 years old female with classic Graves disease

Diagnosis • TSH level usually < 0.05 µu / ml • 95 % of cases, high FT4 & FT3 • In 5% high FT3 with normal T4 (T3 Thyrotoxicosis) • Thyroid receptor (TRAB) are usually elevated at diagnosis • Antibodies against thyroglobulin, peroxidase or both are present in the majority of patients

Diagnosis TSH, free T3&T4 Thyroid antibodies (TSH receptors antibodies) Radionucleotide thyroid scan (inceased uptake)

Treatment Medical: Beta-blockers Carbimazole or Methimazole PTU (propylthiouracil) Other modalities (definitive treatment) Radioactive iodine surgery

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