Thyroid Function Tests in the Newborn

Abstract

. (1970). Archives of Disease in Childhood, 45, 374. Thyroid function tests in the newborn. The 131I triiodothyronine (T3) resin uptake test reflects thyroid function more closely than other acceptable tests currently available.The T3 uptake and protein-bound iodine (PBI) level were estimated in 20 premature and 20 full-term infants at birth and at the end of 1 week.The full-term infant has normal adult values, whereas the premature baby has results extending into the hyperthyroid range at birth, but these fall to within normal limits at 1 week.There are few studies of thyroid function in the newborn and neonatal period of infants bom earlier than the 37th week of gestation. Proteinbound iodine (PBI) levels are similar to those obtained for full-term infants (Danowski et al., 1950). The radioactive iodine (1311) uptake test has limited value because of the risk from irradiation.The in vitro test of radioactive 131I-labelled triiodothyronine uptake using red blood cells was introduced by Hamolsky, Stein, and Freedberg (1957). A similar test was used by later workers using a resin substituted for red blood cells (Nava and De Groot, 1962;Godden and Garnett, 1964 The tests were repeated on the 8th day of life. Plasma-bound iodine was estimated by Auto-analyser The 131I tri-iodothyronine (T,) resin uptake test was estimated after the method of Gimlette (1967). The T, adult euthyroid range is for this laboratory 70-140%.The T3 test can now be performed on as little as 0 1 ml. plasma. ResultsThe PBI levels in both the full-term and premature infants confirm the known high mean and wide ranges of cord blood, with even higher levels at the end of the first week (Table). However, T3 resin uptake is normal for the full-term infants both at birth and at the end of the first week. The premature infants' cord results show a high mean with a very wide range at birth, but by the end of the first week these results also show a normal mean and range.The mean cord blood PBI in both term and premature infants is at the upper limit of adult normal euthyroid values (3*5 fig.-8 0 tzg./100 ml.

Thyroid status in the newborn infant: Effective thyroxine ratio and free thyroxine index

“…Despite these differences between means, only Gray, and Davies (1970) estimated protein-bound iodine and T3 uptake at birth and at 8 days in term and premature infants and found raised values of protein-bound iodine at birth, rising even further on the eighth day. T3 uptake was raised in the premature group at birth, but was otherwise normal.…”

Η Εμβρυομητρικη Σχεσις Της Θυρεοειδικης Λειτουργιας Εν Τερματι Επι Τη Βασει Τωνπαραμετρων Τ_4 (D) Rt_3u T_4rt_3i_x Ft_4f Και Η Επ'αυτων Επιδρασις Της Εφ'απαξ Ενδοφλεβιου Χορηγησεως Ιωδιου

“…Τα ημέτερα αποτελέσματα συμφωνούν απολύτως προς τα βιβλιογραφικά δεδομένα, με μόνην βιβλιογραφικήν εξαίρε σαν τους Chadd καί συν. 38 . Oi τελευταίοι συγγραφείς είς πρόσφατον έργασίαν των (1970) θεωροΰντες ότι ή δοκιμασία τής ύπο τής ρητίνης προσλήψεως της ραδιενεργού τρπωδοθυρονίνης Ι 131 αποτελεί την πλέ ον άξιόλογαν μέθοδον εκτιμήσεως της θυρεοειδικής λειτουργίας, κατα λήγουν, Βάσει των αποτελεσμάτων των, εις το συμπέρασμα ότι αϊ τιμαί της παραμέτρου RT 3 U τών τελειομήνων νεογνών ευρίσκονται εντός των εύθυρεαειδικών πλαισίων τών ενηλίκων.…”