The use of L-T4 as liquid solution improves the practicability and individualized dosage in newborns and infants with congenital hypothyroidism.
Dosage recommendations for the initial therapy of congenital hypothyroidism (CH) in newborns vary between 8 microg/kg/d and 10-15 microg/kg/d.


OBJECTIVE
To evaluate the practicability of LT4 in liquid form and to define the initial dosage for optimal treatment.


METHODS
Liquid LT4 solution was administered to 28 consecutive newborns with primary CH. We measured TSH, T3, T4, free T3 and free T4 before therapy and during follow-up up to 2 years. After 2 years a standardized developmental test (Griffith) was performed.


RESULTS
The median dosage at start of therapy was 12.3 microg LT4/kg/d and decreased to about 5 microg LT4/kg/d after 9 months. The median time of normalization of TSH (< or =6 mU/l) was 2 weeks. In 21 patients, who received a median starting dosage of 12.7 microg LT4/kg (range 9.8-17.1 microg/kg), TSH levels normalized within a median of 1 week. Seven patients receiving only 10.1 microg LT4/kg normalized their TSH only after a median of 2 months.


CONCLUSIONS
Newborns with CH should normalize their TSH within 1-2 weeks. The initial dose necessary to normalize TSH is not lower when a liquid solution is used. The higher dose used in tablets is not due to inefficient absorption, but rather reflects the increased demand for thyroid hormone in the first weeks of life.
Charité, Humboldt-Universität, Pediatric Endocrinology, Otto-Heubner Centrum für Kinder- und Jugendmedizin, Berlin, Germany.
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von Heppe
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Krude
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L'Allemand
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Schnabel
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Grüters
D003409:Congenital Hypothyroidism; D004304:Dosage Forms; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy*; D007223:Infant; D007231:Infant, Newborn; D012996:Solutions; D013974:Thyroxine / Q000008:administration & dosage*
D004304:Dosage Forms; D012996:Solutions; D013974:Thyroxine