Thrombopoietin in the thrombocytopenic term and preterm newborn.
OBJECTIVE
Neonatal thrombocytopenia occurs commonly in neonatal intensive care units. The role of the thrombopoietin (Tpo) system in normal neonatal platelet regulation and neonatal thrombocytopenia is not well understood. The purpose of our study was to: 1) determine the normal Tpo level at birth in healthy nonthrombocytopenic term (NTT) and nonthrombocytopenic preterm (NTP) infants and in infants born to women with preeclampsia; and 2) measure Tpo levels in infants during and after the resolution of thrombocytopenia. Characterizing Tpo levels in the healthy and thrombocytopenic newborn is an important step in furthering our understanding of the pathophysiology of neonatal thrombocytopenia.


METHODS
This study is comprised of 2 parts. For the first part, cord blood was obtained at birth from both term (gestational age [GA]: 38-42 weeks) and preterm (GA: 25-36 weeks) infants. If birth platelet levels were >/=140 x 10(3)/microL and the infant fit criteria for being normal, or if the infant was born to a women with preeclampsia, Tpo levels were measured. For the second part, serial Tpo levels and concomitant platelet counts (Plts) were measured in both preterm and term infants during a period of marked thromboctyopenia (Plt < 100 x 10(3)/microL) until its resolution (Plt >/= 140 x 10(3)/microL).


RESULTS
Median cord blood Tpo levels from NTP infants (n = 35) were higher than those of NTT infants (n = 32; 95 pg/mL vs 48 pg/mL, respectively). In addition, preterm infants born to women with preeclampsia (n = 11) had lower Tpo levels than NTP infants with a similar GA (<41 pg/mL vs 95 pg/mL). For infants with marked thrombocytopenia, median Tpo levels during thrombocytopenia were similar between term (n = 12) and preterm (n = 14) groups (223 pg/mL and 179 pg/mL, respectively), with the majority of individuals showing a decrease in Tpo with resolution of thrombocytopenia. Within each group, there was large variability in the Tpo response to thrombocytopenia.
These data show that the Tpo system is intact in NTP and NTT neonates. Preeclampsia may be an example of a disorder that perturbs this system. The great variability in Tpo levels seen in infants during thrombocytopenia may be related to the mechanism of thrombocytopenia. The finding that, in general, Tpo levels decreased with resolution of thrombocytopenia is consistent with what has been described in adults and children.
Albert
T S
TS
Department of Pediatrics and Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California 94131, USA.
Meng
Y G
YG
Simms
P
P
Cohen
R L
RL
Phibbs
R H
RH
D005260:Female; D005312:Fetal Blood / Q000737:chemistry; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D007235:Infant, Premature, Diseases / Q000097:blood*; D008297:Male; D011225:Pre-Eclampsia; D011247:Pregnancy; D013921:Thrombocytopenia / Q000097:blood*; D013926:Thrombopoietin / Q000097:blood*
D013926:Thrombopoietin