Premium
Hyperthyrotropinemia at 2 weeks of age indicates thyroid dysfunction and predicts the occurrence of delayed elevation of thyrotropin in very low birth weight infants
Author(s) -
Niwa Fusako,
Kawai Masahiko,
Kanazawa Hoshinori,
Iwanaga Kougorou,
Matsukura Takashi,
Hasegawa Takeshi,
Heike Toshio
Publication year - 2012
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/j.1365-2265.2011.04323.x
Subject(s) - medicine , endocrinology , basal (medicine) , trh stimulation test , stimulation , subclinical infection , thyroid , thyrotropin releasing hormone , gestational age , hormone , hypothalamic–pituitary–thyroid axis , pregnancy , thyroid hormones , biology , insulin , genetics
Summary Background For preterm infants, transient hypothyroxinemia of prematurity and transient primary hypothyroidism, especially with delayed elevation of serum thyrotropin (TSH), are important. Methods To address the above two issues, we performed thyrotropin‐releasing hormone (TRH) stimulation tests at about 2 weeks of age for 31 preterm infants with a gestational age of 30 weeks or less. Results For basal TSH levels, 68% of infants (21 of 31) showed normal values (TSH < 10 mU/l) and 32% of infants (10 of 31) showed higher values (four infants: TSH 10–15 mU/l, six infants: TSH > 15 mU/l). Peak TSH values in response to TRH stimulation tests ranged from 9·76 to 114·8 mU/l. All infants showed a significant response to TRH stimulation tests. Only 9·5% of infants (two of 21) with normal basal TSH values showed a hyperresponse (peak TSH > 45 mU/l), whereas 80% of infants (eight of 10) who had higher basal TSH values showed a hyperresponse. All infants who showed mildly elevated basal TSH values (TSH 10–15 mU/l) and a hyperresponse to TRH stimulation tests showed delayed elevation of basal TSH values (TSH > 15 mU/l) later. Conclusions Thyrotropin‐releasing hormone stimulation tests at about 2 weeks of age suggested that the hypothalamic–pituitary–thyroid axis might be established even in extremely premature infants. Basal increased TSH levels (TSH > 10 mU/l) and a hyperresponse to TRH stimulation tests (peak TSH > 45 mU/l) suggested subclinical thyroid dysfunction. Serum TSH values at about 2 weeks of age could be useful for the prediction of delayed TSH elevation.