Objective To investigate the effect of hypothyroxinemia on emotion and hippocampus neurons in developing rats.Methods Sixty-nine healthy postnatal day (PD) 1 rats were randomly divided into control group (n =36) and experimental group (n =33).On PD1,experimental group was bilaterally thyroidectomized to establish hypothyroxinemia model,the control group was only given thyroid exposure operation without thyroid resection.On PD10,21,40,serum triiodothyronine (T3),thyroxine (T4),thyrotropicstimulating hormone (TSH) were detected by radioimmunoassay.Tail suspension test,forced swimming test,the elevated-plus maze and open field were respectively employed to detect the anxiety/depression like behavior on PD30,31,32,33.Nisslg staining was used to determine the survival of neurons at PD10,21,40 in hippocampus CA1,CA3,DG regions.Results Serum T4 levels on PD10,21,40 in experimental group decreased significantly as compared with control group (P ＜0.01),while there was no significant difference in serum T3 or TSH level (P ＞ 0.05).In the tail suspension test,immobility time of experimental group [(197.00 ± 19.50) s] was longer than control group [(158.33 ± 32.90) s,P ＜0.05].In the forced swimming test,immobility time of experimental group[(92.11 ± 35.24) s] was longer than control group [(62.00 ± 23.73) s,P ＜ 0.05].In the elevated plus-maze test,total number of arm entries and closed arm entries in experimental group were increased as compared with control group(P ＜ 0.05),percentage of closed arm/total time of experimental group was decreased as compared with control group(P ＜ 0.05).In the open field,there was no obvious difference between the two groups(P ＞ 0.05).On PD10,21,40,the amount of neurons in DG region of experimental group were less than control group(P ＜0.05),while there was no significant difference in CA1 or CA3 on PD10,21,40(P ＞0.05).Contusions Hypothyroxinemia can cause depression,hyperactivity and hippocampus neuron damage of developing rats.

Objective:To study the factors influencing transient hypothyroxinemia (TH) in one premature twin.Methods:This retrospective study enrolled 283 sets of preterm twins who were born at the gestational age of 26-36 weeks and admitted to the Neonatology Department of the Second Affiliated Hospital of Wenzhou Medical University from June 2009 to September 2021. The levels of thyroxine (T 4), triiodothyronine (T 3) and thyroid stimulating hormone (TSH) were detected at 11-20 d after birth. Finally, 47 sets of twins were further analyzed, in which one twin met the diagnostic criteria of TH (TH group, n=47) and the other twin with exclusion of the diagnosis (control group, n=47). Pearson correlation was used to analyze the correlation of T 4 with gestational age and birth weight. Paired t test, Wilcoxon signed-rank test or McNemar test, and conditional logistic regression were used to analyze the factors influencing TH in premature twins. Results:The gestational age and birth weight of the 47 sets of preterm twins (94 cases) were (31.4±2.3) weeks (26-36 weeks) and (1 611.9±389.3) g (800-2 510 g), respectively. There were 35 sets of dizygotic twins, 11 sets of monozygotic twins, and one set of twins with unknown zygosity. The serum T 4 level in premature infants was positively correlated with the gestational age and birth weight (the correlation coefficients were 0.209 and 0.376, respectively, both P<0.05). Univariate analysis showed that compared with the control group, the factors influencing TH in premature infants ( P<0.1) included female [29.8% (14/47) vs 14.9% (7/47), χ2=3.27 ], bronchopulmonary dysplasia [31.9% (15/47) vs 19.1% (9/47), χ2=3.13], birth weight [(1 547.9±348.0) vs (1 676.0±420.5) g, t=－3.61], white blood cell count [(10.0±3.3)×10 9/L vs (10.9±3.3)×10 9/L, t=－2.19] and vitamin D level [(42.8±12.1) vs (45.9±16.6) nmol/L, t=－1.76]. The data on vitamin D were incomplete and after excluding the factor, the logistic regression showed that female was a risk factor ( OR=18.388 95% CI: 1.317-256.743); while higher birth weight was a protective factor ( OR=0.996, 95% CI: 0.993-0.999). In order to exclude the influence of monozygotic twins on gender, 11 sets of monozygotic twins and one set with unknown zygosity were excluded from multivariate analysis. The results suggested that female was a risk factor ( OR=18.527, 95% CI: 1.209-283.820), while higher birth weight was a protective factor ( OR=0.996, 95% CI: 0.992-1.000). Conclusion:Female and birth weight are the factors influencing TH at 11-20 d after birth in one preterm twin.