Congenital hypothyroidism Flashcards
Causes
A. Primary hypothyroidism:
B. Secondary hypothyroidism
C. Tertiary hypothyroidism:
Primary hypothyroidism
- Thyroid dysgenesis
- Defective thyroid hormone
synthesis (Dyshormonogenesis): - Transient hypothyroidism:
- Maternal iodine deficiency ➡️Endemic goiter
- End organ unresponsiveness to:
- TSH.
- T3 & T4 (Pseudohypothyroidism).
Thyroid dysgenesis:
• The commonest cause (85%).
• Aplasia, hypoplasia or ectopic
gland (may be lingual, sublingual or subhyoid).
Defective thyroid hormone synthesis (Dyshormonogenesis):
- The second common (15%)
- Autosomal recessive disorders
- Associated with goiter.
- Examples:- Iodide transport defect.
- Organification defect: defective thyroid peroxidase enzyme
Transient hypothyroidism:
- Trans placental passage of maternal anti thyroid drugs
* Neonatal iodine containing antiseptics
Secondary hypothyroidism
Due to TSH deficiency either:
- Isolated or.
- With multiple pituitary deficiencies.
Tertiary hypothyroidism:
Due to TSH releasing hormone deficiency
Incidence
1:4000; Female: male = 2:1.
Clinical picture
A. In neonatal period:
- Prolonged physiologic jaundice
- Poor feeding ➡️ chocking spells during feeding.
- Subnormal temperature
- Noisy breathing due to large tongue.
• Abdomen : constipation & umbilical hernia • Lethargy; cry little, sleep much. Widely open posterior and anterior fontanels (Good initial clue) • May be heavier at Birth • May be Limbs and genital edema
Full picture (by end of the 1st year): (cretinism)
- Delayed growth Short stature with persistent infantile proportions
- Delayed mental milestones
- Delayed motor milestones
Head cretinism
• Eyes are puffy, narrow palpebral
fissure
- Broad nose & depressed bridge
- Delayed teething
- Thick large protruding tongue 👅
- coarse brittle hair, low hair line
- delay closer of anterior fontanel
Neck
- Short neck with supraclavicular pad of fat
- Thyroid is enlarged in
Endemic goiter.
Dyshormonogenesis
Pseudohypothyroidism
- Hoarse cry
Cardiac cretinism
Bradycardia
• Pericardial effusion Cardiomegaly
Abdomen cretinism
Protuberant • Umbilical hernia Constipation
Genitalia cretinism
- Delayed maturation
* Rarely precocious puberty
Limbs cretinism
- Short broad hands
- Generalized hypotonia
- Occasional reversible generalized pseudohypertrophy most prominent in calf (Kocher Debre Semelaigne Syndrome)
Skin cretinism
- Cold & pale (resistant anemia)
- Dry (⬆️myxematous tissue)
- May be yellow (⬆️ carotene)
Investigations
- Confirm diagnosis of hypothyroidism
• Low serum free T 4
(In hypothyroidism there’s compensatory increase in peripheral conversion of T 4 to T3 ;
so measuring of T 3 may be misleading)
• Serum TSH
- High in primary hypothyroidism
- Low in secondary and tertiary hypothyroidism.
• In pseudohypothyroidism T4 , T 3 and TSH all are high
Investigations For effect
- Delayed bone age:
- 🤦🏻♀️At birth p absent distal femoral epiphysis (in plane knee radiograph) in 60% of cases (a)
- 🌼Later p delayed appearance of ossific centers (by wrist x-ray)
- Epiphyseal dysgenesis: multiple foci of ossification in heads of femur & humerus (b)
- Skull X-ray p Intrasutural (Wormian) bones (c) and large fontanels
• Beaking of anterior part of T 12 & L 1 vertebrae.
🌼Cardiac
- ECG shows bradycardia and low voltage.
- Echo / Chest x ray may show cardiac enlargement and effusion. Others
- High serum cholesterol/ Macrocytic anemia
Tx
- levothyroxine replacement
- Follow up and monitoring
Prognosis
- Diagnosis & treatment before 3 months p normal linear growth and intelligence
- Delay in diagnosis, failure to correct initial hypothyroxinemia rapidly, inadequate treatment, and poor compliance in the first 2-3 yr of life result in variable degrees of brain damage.
- Without treatment, affected infants are profoundly mentally deficient and growth retarded
- As diagnosis of hypothyroidism is difficult in the first 3 months screening for thyroid function (usually TSH) in all neonates is done in the first week of the life
Treatment with thyroxine should be started befor
2 weeks to 3 weeks of age to reduce the risk of impaired neurodevelopment.
