15.10.5

Question 1

Hypothyroidism

Answer 1

• H-P-T axis is failing or in danger of failing o produce sufficient T4.
• Classified according to :
  ➡️site of abnormality : primary (thyroid), secondary(pituitary) , tertiary (hypothalamus)
  ➡️severity: compensated or decompensated
  ➡️onset: congenital or acquired

Question 2

Congenital hypothyroidism

Answer 2

• One of the more common paediatric endocrinology disorders
• Incidence 1:3500 live births
• Most common preventable cause of learning difficulties
  ➡️MeanIQ=76 (generalpopulationaverageIQ85-115) - IQ > 85 in 78% of those diagnosed <3months old in 0% if diagnosed >7months old
  ➡️additional CNS signs include spasticity, tremor, ataxia and
  sensorineural hearing loss

Question 3

Clinical features of congenital hypothyroidism

Answer 3

• Large tongue
• Coarse facies (flat nose, sunken immature nasal bridge)
• Umbilical hernia
• Irritability
• Lethargy
• Poor growth and weight gain
• Short limbs
• Persistently open post.fontanelle, large ant. fontanelle
• Coarse cry
• Pericardial oedema can be noted on echo in infants
  left for a prolonged period of time.

Clinical features in the neonatal period:
1.Prolonged gestation
2.LBW (large BW)
3.Persistent jaundice
4.Temperature instability
5.Lag in time to initial episode of stooling to more than 20 hrs after birth (delay passing of meconium)
6.Oedema
7.Hypoactivity
8.Poor feeding
ALL these features are NON-SPECIFIC and may not suggest the specific diagnosis to the physician!

Question 4

Causes of congenital hypothyroidism

Answer 4

1. Thyroid dysgenesis (agenesis, hypoplasia, ectopia) - usually sporadic, but can be familial
2. Dyshormogenesis (goitreoften) → inborn errors of thyroid hormone synthesis - Iodine transport defect
   - Organification defect
   - Pendred s.
   - Iodotyrosine deiodinase defect
3. Thyroglobulin defects (goitreoften)
   - mutation of TG gene
4. Transient Hypothyroidism
   - maternal blocking antibodies blocking TSH receptor (mom with auto-immune thyroiditis)
   - Goitrogens: medications eg neomecarzole , certain foods
5. Hypothalamic/pituitaryabnormality
6. Rarercauses-endemiccretinism-foundinareaswithiodine
   deficient but with supplementation of foods e.g. bread and salt , prevalence has decreased.

Question 5

Acquired Hypothyroidism
Prevelance
Causes (Primary, Central)

Answer 5

Prevalence:
- 1: 500 school kids

Causes
Primary
- Hashimoto thyroiditis
- I deficiency (endemic cretinism)
- Removal thyroglossal duct cyst
- Goitrogens: XS I, cabbage, soya
- Drugs: Li, amiodarone
- Infiltrations
- Rx for thyrotoxicosis
- Liver haemangioma
Central
- Any acquired HP cause

Question 6

Clinical Features of Acquired Hypothyroidism

Answer 6

Symptoms
- Cold intolerance
- Weight gain
- Constipation
- Tiredness
- Poor school performance
- Menstrual irregularity

Signs
- Myxoedema (face, wt↑)
- Short/slowing growth
- Goitre
- Dry skin
- Brittle/sparse hair
- Pallor
- Proximal muscle weakness
- Delayed relaxation AJ
- Puberty- delayed/early

Question 7

Thyrotoxicosis
Causes
Incidence

Answer 7

Causes:
- Graves disease
- Thyroiditis:
➡️ Hashimoto
➡️ Subacute
➡️ Purulent
- Toxic nodule(s)
- Thyroid tumour: Adenoma/CA
- TSH driven: Pit tumour
- Pit resistance to T4
- Activating mutation of TSH receptor

Incidence (Graves)
0.8 : 100 000 kids per year

Question 8

Clinical Features of Graves Disease

Answer 8

Symptoms:
- Anxious
- Irritable/emotionally labile
- ↓ school performance/handwriting
- LOW
- Rapid height increase
- Heat intolerance
- Palpitations
- Diarrhoea
- Sleep disturbance
- Menstrual irregulation

Signs
- Goitre
- Exophthalmos
- Tachycardia
- Hypertension
- Tremor, choreiform
- Facial flushing
- Sweatiness
- tall stature
- Thyroid bruit
- Heart murmur

Question 9

Neonatal Thyrotoxicosis
Cause
Prevalence
Clinical
Course

Answer 9

Caues
- Mat TSI (M on Rx or previously Rx)

Prevalence
- GD 1: 2000 pregnancies

Clinical
- Asymptomatic (most)
- Hypothyroid
- Hyperthyroid (<10%) – Mortality <25%

Course
- May start 1-10 days of life
- Self-limiting by 3-12 weeks