Congenital hypothyroidism

Question 1

Causes

Answer 1

A. Primary hypothyroidism:

B. Secondary hypothyroidism

C. Tertiary hypothyroidism:

Question 2

Primary hypothyroidism

Answer 2

1. Thyroid dysgenesis
2. Defective thyroid hormone
   synthesis (Dyshormonogenesis):
3. Transient hypothyroidism:
4. Maternal iodine deficiency ➡️Endemic goiter
5. End organ unresponsiveness to:
   - TSH.
   - T3 & T4 (Pseudohypothyroidism).

Question 3

Thyroid dysgenesis:

Answer 3

• The commonest cause (85%).

• Aplasia, hypoplasia or ectopic
gland (may be lingual, sublingual or subhyoid).

Question 4

Defective thyroid hormone synthesis (Dyshormonogenesis):

Answer 4

• The second common (15%)
• Autosomal recessive disorders
• Associated with goiter.
• Examples:- Iodide transport defect.
• Organification defect: defective thyroid peroxidase enzyme

Question 5

Transient hypothyroidism:

Answer 5

• Trans placental passage of maternal anti thyroid drugs

* Neonatal iodine containing antiseptics

Question 6

Secondary hypothyroidism

Answer 6

Due to TSH deficiency either:
- Isolated or.

• With multiple pituitary deficiencies.

Question 7

Tertiary hypothyroidism:

Answer 7

Due to TSH releasing hormone deficiency

Question 8

Incidence

Answer 8

1:4000; Female: male = 2:1.

Question 9

Clinical picture

A. In neonatal period:

Answer 9

• 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

Question 10

Full picture (by end of the 1st year): (cretinism)

Answer 10

• Delayed growth Short stature with persistent infantile proportions
• Delayed mental milestones
• Delayed motor milestones

Question 11

Head cretinism

Answer 11

• 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

Question 12

Neck

Answer 12

• Short neck with supraclavicular pad of fat
• Thyroid is enlarged in

Endemic goiter.

Dyshormonogenesis

Pseudohypothyroidism

• Hoarse cry

Question 13

Cardiac cretinism

Answer 13

Bradycardia

• Pericardial effusion Cardiomegaly

Question 14

Abdomen cretinism

Answer 14

Protuberant • Umbilical hernia Constipation

Question 15

Genitalia cretinism

Answer 15

• Delayed maturation

* Rarely precocious puberty

Question 16

Limbs cretinism

Answer 16

• Short broad hands
• Generalized hypotonia
• Occasional reversible generalized pseudohypertrophy most prominent in calf (Kocher Debre Semelaigne Syndrome)

Question 17

Skin cretinism

Answer 17

• Cold & pale (resistant anemia)
• Dry (⬆️myxematous tissue)
• May be yellow (⬆️ carotene)

Question 18

Investigations

1. Confirm diagnosis of hypothyroidism

Answer 18

• 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

Question 19

Investigations For effect

Answer 19

• 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

Question 20

Tx

Answer 20

• levothyroxine replacement

- Follow up and monitoring

Question 21

Prognosis

Answer 21

• 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

Question 22

Treatment with thyroxine should be started befor

Answer 22

2 weeks to 3 weeks of age to reduce the risk of impaired neurodevelopment.