Hypothyroxinemia in very low birth weight infants and its effect on early postnatal feeding and weight gain / 中华围产医学杂志

ABSTRACT

Objective:To investigate the incidence of hypothyroxinemia in very low birth weight infant (VLBWI) and its effect on early postnatal feeding and weight gain.Methods:This retrospective study analyzed 164 cases of VLBWIs admitted to the Neonatal Intensive Care Unit of Peking University First Hospital from January 2017 to December 2018. According to the gestational age, these VLBWIs were divided into <30 weeks group ( n=85) or ≥30 weeks group ( n=79), and the basic data and thyroid function were compared. According to the levels of serum tetraiodothyronine and free tetraiodothyronine at the first thyroid function test, the subjects were further assigned into normal thyroxine group and hypothyroxinemia group. The risk factors of hypothyroxinemia identified at the first detection were analyzed by single and multiple-facter analysis. The results of the second detection of thyroxine were also analyzed. On the basis of the first detection and receiving treatment or not, the <30 weeks and ≥30 weeks groups were divided into normal thyroxine, hypothyroxinemia treated and hypothyroxinemia untreated subgroups, and differences in the tolerance of early feeding and weight gain were compared between different groups. Two independent samples/paired t-test, rank sum test, Chi-square test and logistic regression were used for statistical analysis. Results:Out of the 164 VLBWIs with the gestational age of (29.7±2.0) weeks and birth weight of (1 210±210) g, 27 cases (16.5%) were extremely low birth weight infants. The age at their first detection was (10.7±3.1) d and the incidence of hypothyroxinemia was 45.1% (74/164), including 71 mild and three severe cases, with a higher incidence in the ≥30 weeks group comparing to the <30 weeks group [55.7%(44/79) vs 35.5%(30/85), χ 2= 6.883, P=0.009]. All the three severe cases were in the ≥30 weeks group. The gestational age ( OR=1.413, 95% CI1.044-1.912, P=0.025) and male infant ( OR=2.082, 95% CI 1.047-4.143, P=0.037) were the risk factors of hypothyroxinemia. At the second detection, the incidence of hypothyroxinemia in VLBWIs with normal thyroid function at their first test was 47.6% (39/82), which is higher in the ≥30 weeks group than in the <30 weeks group [64.5%(20/31) vs 37.3%(19/51), χ 2= 5.745, P=0.017]. Among the infants with hypothyroxinemia at the first detection, those untreated had a significantly higher incidence of hypothyroxinemia at the second detection than those treated [81.3%(26/32) vs 38.7%(12/31), χ 2= 11.905, P=0.001]. The incidence of abdominal distension within 21 days, feeding volume on day 7, 14, and 21, and neonatal weight gain within 7, 14, and 21 days were similar between normal thyroxine, hypothyroxinemia treated and hypothyroxinemia untreated subgroups within the ≥30 weeks or the <30 weeks groups (all P>0.05). Conclusions:VLBWI is at high risk of hypothyroxinemia. Two times of postnatal thyroid function tests can help to detect the delayed hypothyroxinemia. Thyroxine level and receiving treatment or not may have no significant effect on the early postnatal feeding and weight gain.