Neonatal hyperthyrotropinemia is associated with low birth weight: a twin study

Evolution of Subclinical Hypothyroidism Diagnosed in the First 3 Months of Life in Newborns Living in North Italy: A Retrospective Cohort Study

BACKGROUND

Subclinical hypothyroidism (SH) management in neonatal age opens important questions. We aimed to describe the evolution over time of subclinical hypothyroidism diagnosed in the first three months of life in a population of full-term neonates.

METHODS

A single-center longitudinal retrospective cohort study in a tertiary care center was conducted. We recruited 32 subjects with SH diagnosed within the first three months of life. We collected clinical, biochemical, and ultrasound data for every subject at the first examination and every six months until four years of age.

RESULTS

A total of 43.8% of subjects showed stimulating thyroid hormone (TSH) levels over the limit of 10 mUI/L and underwent treatment (Group 1). Eleven subjects started therapy at the first visit, while three subjects started it after a period of observation; 15.6% (Group 2A) showed a trend of TSH decrease and were finally discharged from the follow-up, while 40.6% (Group 2B) showed a TSH level slightly increased, changeless over time.

CONCLUSIONS

We demonstrated that more than half of newborns with hyperthyrotropinemia did not require substitutive therapy showing a positive trend toward normalization or a remaining slight increase compared to normal levels. Moreover, our study suggests the need for a follow-up over time to check the TSH levels course.

Thyroid Dysfunction and the Effect of Iodine-Deficient Parenteral Nutrition in Very Low Birth Weight Infants: A Nationwide Analysis of a Korean Neonatal Network Database

Background: To investigate the impact of nutritional iodine deficiency on thyroid dysfunction (TD) in very low birth weight (VLBW) infants, we analyzed the association between iodine-deficient parenteral nutrition (PN) and TD requiring L-thyroxine (TD-LT4). Methods: Data of VLBW infants were obtained from the Korean Neonatal Network registry. Factors including duration of PN were analyzed according to TD-LT4. Results: TD-LT4 occurred in 490 (8.7%) of 5635 infants, and more frequently occurred in infants requiring PN for ≥4 weeks (10.2%). PN ≥ 4 weeks was one of the risk factors for TD-LT4, with an odds ratio (OR) of 1.346, p = 0.002. However, multivariate analysis showed that TD-LT4 was more of a risk for infants that were small for gestational age (OR 2.987, p < 0.001) and for other neonatal morbidities such as seizures (OR 1.787, p = 0.002) and persistent pulmonary hypertension (OR 1.501, p = 0.039) than PN ≥ 4 weeks (OR 0.791, p = 0.080). Conclusions: Prolonged iodine-deficient PN might affect TD-LT4 in VLBW infants. However, the effect of nutritional iodine deficiency on TD-LT4 risk was less than that of SGA or severe neonatal morbidities in Korean VLBW infants.

Guideline for the Treatment of Hypothyroidism in Prematurity

Congenital hypothyroidism is one of the most common endocrine disorders in infants and children. Thyroid hormone effects the function of most organs of the body. In premature neonates, thyroid abnormalities are very common but transient. There is a significant difference between the appropriate time for screening in premature and term neonates and there are different viewpoints in treating hypothyroidism in prematurity. According to the probable exceptions in this issue, there is no definite guideline. Therefore, regarding this confusion, this guideline aimed to help clinicians for rapid on-time decision making.

Multivariate Analysis of Thyrotropin in Preterm Newborns Based on Adequacy of Weight for Gestational Age

BACKGROUND

Different and conflicting data have been published concerning thyrotropin (TSH) levels among small-for-gestational-age (SGA) and appropriate-for-gestational-age (AGA) newborns. The hypothesis of this study was that SGA preterm infants have higher TSH levels than those who are not underweight do.

METHODS

This cross-sectional study analyzed the TSH levels of all preterm newborns with a negative congenital hypothyroidism screening result (TSH <7.5 μIU/mL). Secondary variables were sex, birth weight (SGA, AGA), days of life at blood extraction, maternal origin, gestational age, and being a twin or not. Two multiple linear regression models were constructed comparing TSH levels in SGA and AGA or the z-score for birth weight and the remaining variables.

RESULTS

A sample including 5819 preterm infants was obtained: 53.8% male, 23.3% twins, and 3.3% SGA. TSH concentrations were 2.16 ± 2.0 μIU/mL for the SGA infants and 1.80 ± 1.5 μIU/mL for the AGA infants (p = 0.012), with a negative correlation (p < 0.001) between TSH levels and the z-score for the weight of the newborn. The multivariate analysis comparing TSH levels between SGA and AGA gave the following: SGA (B = 0.46, p < 0.001), Latin American mother (B = -0.16, p = 0.029), days of life at blood extraction (B = -0.26, p < 0.001), and gestational age ≤28 weeks (B = -0.56, p < 0.001). Using the z-score for the weight, the associations were: maternal origin North Africa (B = 0.19, p = 0.042), days of life at blood extraction (B = -0.27, p < 0.001), gestational age ≤28 weeks (B = -0.55, p < 0.001), and z-score for weight (B = -0.12, p < 0.001).

CONCLUSIONS

Our multivariate analysis suggests that TSH concentrations are higher in SGA infants than they are in AGA infants, and this should be taken into account when establishing a reference interval appropriate for this population. The clinical relevance remains unknown, but lines of research are opened that may allow a better understanding of the long-term morbidities in these newborns.

Characteristics of Delayed Thyroid Stimulating Hormone Elevation in Neonatal Intensive Care Unit Newborns

OBJECTIVES

To elucidate the incidence, clinical characteristics, and short-term outcome of delayed thyroid stimulating hormone (TSH) elevation (dTSH) in a large cohort of newborns admitted to the neonatal intensive care unit.

STUDY DESIGN

Data were gathered from a cohort of 13 201 newborns admitted to the neonatal intensive care unit born between January 1, 2008, and October 31, 2014, who underwent TSH measurements because of low T4 levels on the second screen. The data from the newborn screening program included gestational age, birth weight (BW), T4 levels, and short-term outcome.

RESULTS

Of 13 201 newborns, 333 (1:40) presented with dTSH (TSH >15 IU/L). dTSH had a peak proportion at gestational age of 37-39 weeks, and 66% of the patients had BW >1500 g. T4 levels in the 333 patients were negatively correlated with TSH levels (R = -0.505; P < .001), and significantly lower than levels in the other newborns: 5.9 ± 2.8 vs 7.6 ± 1.7 µg/dL; P < .001. TSH levels in dTSH newborns were already higher on the initial screen compared with the other newborns: 8.3 ± 5.2 vs 4.2 ± 3.7 IU/L; P < .001. Fifty-eight percent of 193 patients with dTSH were started on levothyroxine treatment.

CONCLUSIONS

dTSH has a higher incidence than previously reported, especially among newborns with BW >1500 g. Relatively high TSH and low T4 levels on the initial and second screen respectively are predictors for dTSH. Levothyroxine treatment is required in most cases.

Incidence and Interrelated Factors in Patients With Congenital Hypothyroidism as Detected by Newborn Screening in Guangxi, China

Background. A newborn screening program (NSP) for congenital hypothyroidism (CH) was carried out in Guangxi in order to understand the incidence of CH and the factors interrelated to major types of CH in this region of China. Methods. During 2009 to 2013, data from 930 612 newborns attending NSP in Guangxi were collected. Patients were classified with either permanent CH (PCH) or transient CH (TCH) after 2 years of progressive study. Results. A total of 1210 patients were confirmed with CH with an incidence of 1/769, including 68 PCH and 126 TCH cases with incidences of 1/6673 and 1/3385, respectively. The frequency of thyroid stimulating hormone values greater than 5 mIU/L was 7.2%, which, based on WHO guidelines, suggests that the population was mildly iodine deficient. Conclusions. The incidence of CH was high in Guangxi. Approximately two thirds of CH patients were TCH, which may be due to a deficiency in iodine within the population.