Treatment of Congenital Iodine-Deficiency in Confirmed Primary Hypothyroidism
This protocol covers the management of congenital iodine-deficiency in neonates in whom primary hypothyroidism has been biochemically confirmed — whether on routine neonatal screening or on subsequent thyroid function testing.
Clinical scenario
Serum fT4 below the age-specific reference interval with serum TSH clearly above the age-specific reference interval; or serum TSH >20 mU/L at confirmatory testing; or, where thyroid function tests are unavailable, filter paper TSH >40 mU/L at neonatal screening.
Treatment approach
Oral thyroid hormone replacement, initiated as soon as possible after confirmed diagnosis, is the recommended intervention. The dosing approach is calibrated to the severity of biochemical findings at presentation — the complete starting-dose algorithm, adjustment criteria, and monitoring schedule are detailed in the full regimen.
Treatment goals
Rapid normalization of serum TSH within the age-specific reference interval — with serum fT4 maintained in the upper half of the age-specific reference interval — to optimise neurodevelopmental outcomes.
References
DOI: 10.1089/thy.2020.0333
- If the serum fT4 concentration is below and TSH clearly above the age-specific reference interval, then levothyroxine (LT4) treatment should be started immediately.
- If the serum TSH concentration is >20 mU/L at confirmatory testing (approximately in the second week of life), treatment should be started, even if fT4 is normal (arbitrary threshold, expert opinion).
- In countries or regions where thyroid function tests are not readily available, LT4 treatment should be started if filter paper TSH concentration is >40 mU/L (at the moment of neonatal screening; arbitrary threshold, expert opinion).
- LT4 alone is recommended as the medication of choice for the treatment of CH.
- LT4 treatment should be started as soon as possible, not later than 2 weeks after birth or immediately after confirmatory (serum) thyroid function testing in neonates in whom CH is detected by a second routine screening test.
- The first treatment goal in neonates with primary CH is to rapidly increase the circulating amount of thyroid hormone, reflected by normalization of serum TSH; thereafter, TSH should be kept within the reference interval.
- Rapid normalization of TSH and keeping fT4 in the upper half of the age-specific reference interval have been shown to optimize the neurodevelopmental outcome.
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