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10. What is transient congenital hypothyroidism?

Transient congenital hypothyroidism is defined as abnormal thyroid pro-

file on neonatal screening (low T 4 and high TSH), with normalization of

thyroid function after 1–2 months of age. The causes of transient congeni-

tal hypothyroidism include maternal/fetal iodine deficiency or excess,

fetal exposure to maternal antithyroid drugs, transplacental passage of

maternal thyrotropin receptor-blocking antibodies (TRAbs), heterozy-

gous mutations of DUOX2/DUOXA2, and congenital hepatic

hemangioma.

11. Why do patients with hepatic hemangioma have hypothyroidism?

Patients with hepatic hemangioma express type 3 deiodinase enzyme, which

converts T 4 to reverse T 3. This results in reduced levels of T 4 and T 3 and conse-

quently “consumptive” hypothyroidism. This is a rare cause of hypothyroidism

and is considered as a paraneoplastic manifestation of hemangiomas.

Consumptive hypothyroidism is usually seen in infants, although a few cases

have also been described in adults. These patients require therapy with large

doses of L-thyroxine for normalization of serum T 4. The disorder is self-limit-

ing and usually abates by the age of 5–6 years.

Neonatal Screening

Dried blood spot

TSH (D2/D3 of life)

TSH>40 μIU/ml

Venous sample

FT4 and TSH

Start treatment

TSH<40 μIU/ml

TSH>20 μIU/ml

Start treatment

TSH 6-20 μIU/ml

Low FT4

(<0.8 ng/dl)

Start treatment

TSH 6-20 μIU/ml

Normal FT4

Diagnostic imaging

Retesting after

2 weeks

Or start treatment

and reassess later

Venous sample

FT4 and TSH

Fig. 3.4 Screening and management strategies for congenital hypothyroidism

3 Thyroid Disorders in Children