Clinical importance of hypothyroxinemia in the preterm infant and a discussion of treatment concerns

Abstract

With 25 000 neonates born in less than 28 weeks each year in the USA, the economic impact of the very high rates of cognitive disabilities and related neurological dysfunction in survivors is substantial. The lifetime direct and indirect costs of CP are estimated at US$1 million per person and the costs of mental retardation are even higher. If reversal of transient hypothyroxinemia proves effective in reducing the risks of CP or mental retardation in ELGANs by 30%, we estimate an overall saving of US$ 3 billion per year. There is a pressing need for a phase III trial of thyroid hormone that is of sufficient duration and size to determine whether a clinically important reduction in risk of developmental impairments in ELGANs can be achieved.

Congenital hypothyroidism

“…More questions about the potential negative effects of excess thyroid hormone were raised by a recent study of preterm infants. Preterm and LBW infants commonly manifest a pattern of low T4 and normal TSH termed 'transient hypothyroxinemia of prematurity' (THOP) [32]. Although THOP is associated with poor medical and neurodevelopmental outcomes [33], a causal relationship has not been established, and the few existing trials of treatment for THOP have not demonstrated a clear benefit [34][35][36].…”

Thyroid Stimulating Hormone and Thyroxine Screening in the Preterm Newborn: Reference Values

“…Tuttavia è determinante per il clinico avere un punto di riferimento preciso da cui partire, per stabilire se i livelli di TSH e T4 di un determinato bambino incrementano o diminuiscono nei giorni successivi alla nascita. I lavori svolti, concernenti la somministrazione di ormoni tiroidei alla nascita nel neonato pretermine, hanno dimostrato risultati discordanti, per quanto riguarda sia il deficit neurocognitivo di tali soggetti, sia l'incidenza di distress respiratorio e di BPD [11][12][13][14][15][16][17][18][19][20]. Attualmente infatti non esistono indicazioni precise, in rapporto agli studi effettuati, per somministrare gli ormoni tiroidei a tutti i soggetti ELGAN.…”

“…Per tali motivi alcuni AA. hanno prospettato la necessità di somministrare ormoni tiroidei fin dai primi giorni di vita nel neonato di età gestazionale estremamente bassa (ELGAN) [10][11][12][13][14][15][16][17][18][19][20]. Tuttavia non sono presenti in letteratura lavori che abbiano valutato in 2°-3° giornata di vita, momento in cui i fenomeni di adattamento neonatale sono ormai completati, i livelli di TSH e tT4 in un numero sufficientemente ampio di soggetti ELGAN, suddivisi in varie fasce di età gestazionale (EG).…”

Wrodzona niedoczynność tarczycy — polskie rekomendacje dotyczące leczenia, monitorowania terapii i badania przesiewowego w specjalnych kategoriach noworodków z wysokim ryzykiem niedoczynności tarczycy

“…cerebral palsy [13,[37][38][39][40][41]. In the study groups with a positive effect of L-thyroxine on the development of preterm babies, a dose of 6-8 μg/kg body weight was used, slightly improving mental development after 5-10 years.…”

“…Niemniej liczne kohortowe badania retrospektywne dokumentują związek między hipotyroksynemią i opóźnieniem rozwoju psychoruchowego wcześniaków oraz występowaniem w tej grupie mózgowego porażenia dziecięcego [13,[37][38][39][40][41]. W dotychczas obserwowanych grupach, w których stwierdzono pozytywny wpływ leczenia L-tyroksyną na rozwój wcześniaków, stosowano dawkę 6-8 μg/kg masy ciała, co powodowało nieco lepszy rozwój umysłowy widoczny po 5-10 latach.…”