Clinical_Rounds_in_Endocrinology_Volume_II_-_Pediatric_Endocrinology

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19. How to approach a newborn with congenital hypothyroidism?

Thyroid radionuclide uptake and scan ( 99m Tc pertechnetate/^123 I scan) is the

preferred first-line investigation in a newborn with primary CH, and this

can be done even within a week after initiation of L-thyroxine therapy. An

approach to newborn with congenital hypothyroidism is shown in the fig-

ure given below. If a child was not evaluated for the etiology of congenital

hypothyroidism before initiation of therapy, L-thyroxine should not be dis-

continued, and the child may be reevaluated after 3 years of age (Fig. 3.8 ).

Fig. 3.7 99m Tc
pertechnetate scan
demonstrating no tracer
uptake in the thyroid
region or along the line of
descent of the gland in a
child with congenital
hypothyroidism due to
thyroid aplasia

Primary Congenital Hypothyroidism

Thyroid radionuclide uptake and scan (99mTc pertechnetate/^123 I scan)

No uptake

Ultrasonography of neck

No thyroid tissue

Serum Thyroglobulin

Absent

Thyroid aplasia Apparent athyreosis

Detectable

Thyroid tissue present

• TSH-β gene mutation


• TSH receptor gene mutation


• Maternal TSH blocking antibody


• NIS defect


• Iodine excess

*Ultrasonography is complementary

• Ectopic thyroid gland


• Dyshormonogenesis


• Maternal anti-thyroid drugs


• Iodine deficiency

Uptake normal/increased*

Fig. 3.8 Diagnostic approach to a child with primary congenital hypothyroidism

3 Thyroid Disorders in Children