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- How to treat congenital hypothyroidism?
The goal of therapy in congenital hypothyroidism is normalization of T 4 /FT 4
and TSH as rapidly as possible (T 4 /FT 4 within 2 weeks and TSH within a
month) for normal growth and development. Oral L-thyroxine (L-T 4 ) is the
therapy of choice for congenital hypothyroidism. Although T 3 is required for
neuronal growth and development, T 3 in brain is predominantly derived from
local deiodination of circulating T 4 ; hence therapy with T 3 is not recommended.
L-thyroxine should be initiated at a dose of 10–15 μg/Kg/day for infants aged
0–3 months, 8–10 μg/Kg/day for 4–6 months, and 6–8 μg/Kg/day for infants of
7–12 months. The tablet must be crushed and mixed with breast milk/formula
feed/water before administration. L-thyroxine tablet should not be mixed with
preparations containing iron/calcium/soya as they interfere with the absorption
of L-T 4.- How to monitor a newborn with congenital hypothyroidism on L - thyroxine
therapy?
After initiation of therapy, infants should be closely followed up with estima-
tion of T 4 /FT 4 and TSH every fortnightly till T 4 /FT 4 and TSH are normalized
and, thereafter, one to three monthly till 12 months of age. After infancy, child
can be followed up every 2–3 monthly till 3 years of life. Sample for thyroid
profi le can be taken either before the administration of next dose or at least 4h
after intake of L-thyroxine. TSH should be maintained in the age-specifi c nor-
mal range and T 4 /FT 4 in the upper half of age-specifi c normal range. The rec-
ommended cutoffs are TSH 0.5–2.5 μIU/ml and T 4 between 10 and 16 μg/dl (or
FT 4 1.4–2.3 ng/dl) during fi rst 3 years of life; thereafter TSH alone can be
monitored every 3–6 months and maintained between 0.5 and 2.5 μIU/ml.
However, it should be noted that some infants may have TSH above the refer-
ence range, despite having T 4 /FT 4 above age-specifi c normal range. This is
possibly because of resetting of hypothalamo–pituitary–thyroid axis as a result
of long-standing hypothyroidism during intrauterine life. Linear growth and
milestones should be regularly monitored in children with congenital hypothy-
roidism on therapy. In addition, periodic assessment for hearing is also essential
in these children. - What is the neurological outcome of newborns with congenital
hypothyroidism?
It is important to initiate therapy as early as possible (preferably within 2 weeks
of birth) in newborns with congenital hypothyroidism for optimal neurocogni-
tive development. It has been shown that early therapy is associated with near-
normal intellectual outcome. However, newborns with severe congenital
hypothyroidism (as evidenced by athyreosis, absent distal femoral epiphysis,
FT 4 <0.38 ng/dl, and signifi cantly elevated TSH), delay in initiation of L-T 4
3 Thyroid Disorders in Children