Reference intervals for thyroid function from the fifth to seventh day of life in twin-pregnancy preterm neonates: an 8-year retrospective study

• Published in: Hormones (Athens, Greece) Vol. 23; no. 2; pp. 235 - 244
• Main Authors: Zheng, Xin-Ting, Lin, Xin, Ma, Mei, Lai, Shu-Hua, Yang, Chang-Yi
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.06.2024
• Subjects: Endocrinology; Female; Gestational Age; Humans; Infant, Newborn; Infant, Premature - blood; Male; Medicine; Medicine & Public Health; Metabolic Diseases; Original Article; Pregnancy; Pregnancy, Twin - blood; Pregnancy, Twin - physiology; Reference Values; Retrospective Studies; Thyroid Function Tests - standards; Thyroid Gland - physiology; Thyrotropin - blood; Thyroxine - blood; Triiodothyronine - blood; Twin-pregnancy; Thyroid function; Fifth to seventh day of life; Reference intervals; Preterm
• ISSN: 1109-3099; 2520-8721; 2520-8721
• DOI: 10.1007/s42000-024-00547-w

Purpose The immature and developing hypothalamic-pituitary-thyroid axis leads to different levels of thyroid function in twin neonates, including free thyroxine (FT4), free triiodothyronine (FT3), and thyroid stimulating hormone (TSH) levels. No reference intervals for twins have been established until now. To compensate for this lack, we collected data and established this standard across different gestational ages (GAs) and sexes. Methods A total of 273 pairs of neonates admitted to the NICU in Southeast China from 2015 to 2022 were included. Each pair was divided into Neonate A (relatively heavy birth weight (BW)) and Neonate B (relatively light BW). Their thyroid functions were analyzed to establish reference intervals and comparisons were made stratified by GA and sex. Results The FT3, FT4, and TSH reference intervals in twin neonates with a GA of 26–36 weeks were as follows: Neonate A and B: 3.59 ± 0.99 and 3.57 ± 1.00 pmol/L; Neonate A and B: 17.03 ± 5.16 and 16.77 ± 5.29 pmol/L; and Neonate A and B: 4.097 ± 3.688 and 4.674 ± 4.850 mlU/L, respectively. There were significant differences between serum FT3 and FT4 reference intervals and GA ( p  < 0.05). The serum FT3 and FT4 reference intervals for male neonates were lower than those for female neonates in the 29–32-week group ( p  < 0.05). Conclusion This was the first study, to our knowledge, to establish reference intervals for thyroid function in twin neonates from the fifth to seventh day of life, which will be beneficial for the diagnosis and management of congenital hypothyroidism.