Congenital hypothyroidism with delayed thyroid-stimulating hormone elevation in premature infants born at less than 30 weeks gestation

Abstract

Thyroid dysfunction is common among premature infants born before 30 weeks gestation. The majority of cases with thyroid dysfunction had CH with delayed TSH elevation, which was not detected by NBS. We recommend measurement of serum TSH and free T4 levels on day of life 30 in premature infants born at <30 weeks gestation to identify patients with CH with delayed TSH elevation.

Small for gestational age is a risk factor for the development of delayed thyrotropin elevation in infants weighing less than 2000 g

“…Multiple gestation, birthweight, gestational weeks and the 5‐minute Apgar score have been associated with the development of dTSHe in a previous report on infants born at <30 weeks of gestation . In the present study, these were not identified as independent risk factors for dTSHe, possibly we examined them according to birthweight, and not according to weeks of gestation.…”

“…Multiple gestation, birthweight, gestational weeks and the 5-minute Apgar score have been associated with the development of dTSHe in a previous report on infants born at <30 weeks of gestation. 8 In the present study, these were not identified as independent risk factors for dTSHe, possibly we examined them according The present study focused on infants with a birthweight <2000 g, as a second neonatal screening is performed in Japan when the birthweight is <2000 g. 10 As mentioned above, the Japanese guidelines recommend that the timing of the second screen is at the earliest possible time according to the following schedules: 1 month after birth, when the infant's body weight reaches 2500 g, or at discharge from the hospital. According to the recommendation, the second screening should be performed within 30 days; however, in the present study, the median age for performing the second screening was 37 days.…”

“…Delayed thyrotropin (TSH) elevation (dTSHe) is characterised by the development of a raised TSH level after initial screening had shown a value was below the laboratory cut‐off for first newborn screening . dTSHe is common in infants born at <33 gestational weeks and low birthweight infants . For this reason, the Japanese guidelines for the newborn screening for congenital hypothyroidism (CH) recommend a second screening to detect dTSHe in infants with a birthweight <2000 g .…”

“…However, approximately two‐thirds of tertiary neonatal intensive care units (NICUs) in Japan perform a thyroid function test separately from the newborn thyroid screening, as an elevation in the TSH level may be recognised in some infants before the second screening . Several risk factors for the development of dTSHe have been identified, according to various conditions, such as <30 gestational weeks, hospitalisation in the NICU, cardiac diseases, vancomycin use, insulin use and furosemide use . However, reports identifying risk factors according to infants with a birthweight of <2000 g are lacking.…”

“…11 Several risk factors for the development of dTSHe have been identified, according to various conditions, such as <30 gestational weeks, hospitalisation in the NICU, cardiac diseases, vancomycin use, insulin use and furosemide use. 3,8,9 However, reports identifying risk factors according to infants with a birthweight of <2000 g are lacking. Detection of risk factors might be helpful in the early diagnosis and intervention of dTSHe.…”