Trimester-Specific Reference Intervals for Thyroid Function Parameters in Indian Pregnant Women during Final Phase of Transition to Iodine Sufficiency

Thyroid Function Test in Preterm Neonates: Normative Data

Introduction

Initial surge of thyroid-stimulating hormone (TSH) in neonates increases free and total triiodothyronine (T3) and tetraiodothyronine (T4) in 24-36 hours following birth, and the effect then gradually wanes off. As somatic and intellectual development is dependent on normal thyroid function especially in infancy, normative data in these children may be of immense value to diagnose hypothyroidism in this subset of infants. Comprehensive normative values of thyroid function parameters in preterm neonates are scarcely available. The objective of this study was to determine the normative value of thyroid function parameters in preterm neonates.

Methods

Preterm neonates (n = 102) born at 34 and 35 weeks of gestation of euthyroid mothers from an iodine-sufficient population were evaluated for T3, T4, free thyroxine (FT4) and TSH during 3-7 days after birth and again after 1 month. The expected date of delivery (EDD) and Ballard score were used to identify the duration of gestation.

Results

The mean gestational age was 34.7 ± 0.41 weeks. The mean (± SD) for T3 (ng/dl), T4 (μg/dl), FT4 (ng/ml) and TSH (μIU/ml) on days 3-7 following birth was as follows: 156 ± 44.6, 12.8 ± 3.7, 1.50 ± 0.54 and 7.13 ± 6.04, respectively. Around 4 weeks of age, values changed to 104 ± 38.4, 12.1 ± 4.02, 1.46 ± 0.42 and 3.25 ± 2.85, respectively. All parameters changed significantly around 4 weeks, except FT4. None of the parameters were correlated with gestational age or body weight at birth. Normative values for each parameter in percentiles were generated.

Conclusion

This study generated the normative values of the thyroid function test during the first week and after around 4 weeks of life for premature neonates (born at 34-35 weeks).

Regulation and safety measures for nanotechnology-based agri-products

There is a wide range of application for nanotechnology in agriculture, including fertilizers, aquaculture, irrigation, water filtration, animal feed, animal vaccines, food processing, and packaging. In recent decades, nanotechnology emerged as a prospective and promising approach for the advancement of Agri-sector such as pest/disease prevention, fertilizers, agrochemicals, biofertilizers, bio-stimulants, post-harvest storage, pheromones-, and nutrient-delivery, and genetic manipulation in plants for crop improvement by using nanomaterial as a carrier system. Exponential increase in global population has enhanced food demand, so to fulfil the demand markets already included nano-based product likewise nano-encapsulated nutrients/agrochemicals, antimicrobial and packaging of food. For the approval of nano-based product, applicants for a marketing approval must show that such novel items can be used safely without endangering the consumer and environment. Several nations throughout the world have been actively looking at whether their regulatory frameworks are suitable for handling nanotechnologies. As a result, many techniques to regulate nano-based products in agriculture, feed, and food have been used. Here, we have contextualized different regulatory measures of several countries for nano-based products in agriculture, from feed to food, including guidance and legislation for safety assessment worldwide.

First-Trimester Reference Intervals for Thyroid Function Testing among Women Screened at a Tertiary Care Hospital in India

Objectives  Due to differences in the method of assay and population-specific factors, each laboratory needs to establish its own gestation-specific reference intervals (GRIs) for thyroid hormones.

Materials and Methods  Three-hundred forty-one women with less than 14 weeks gestation were screened at a tertiary care hospital in Chhattisgarh, India. Serum levels of thyroid-stimulating hormone (TSH), free thyroxine (fT4), and thyroid peroxidase antibody (anti-TPO) were measured using an ADVIA Centaur XP immunoassay.

GRIs (2.5th and 97.5th percentiles) were determined for TSH and fT4. TSH and fT4 concentrations were converted to multiples of the median (MoM) values. Effect of maternal age, gestational age, and maternal weight was analyzed.

Statistical Analysis  Quantitative variables were expressed as means and standard deviations (SD), and qualitative variables were expressed as frequencies and percentages. Normality of the data was checked using the Kolmogorov–Smirnov test. Values that were normally distributed were expressed only as means and SD. Those that were not normally distributed were expressed as medians and interquartile range. For all statistical analysis, p  < 0.05 was considered as statistically significant.

Results  First-trimester GRI was 0.245 to 4.971 mIU/L for TSH, 10.2 to 18.9 pmol/L for fT4, and 27.0 to 56.89 kIU/L for anti-TPO. There was no significant difference in the mean serum TSH ( p  = 0.920), fT4 ( p  = 0.714), or anti-TPO ( p  = 0.754) values among women in 4 to 7th week and 7 to 14th week of gestation. The 1st and 99th centile MoMs were 0.03 and 4.09 for TSH and 0.66 and 1.39 for fT4. There was a significant positive correlation between the maternal weight and TSH MoM values ( p  = 0.027, r  = 0.120).

Conclusion  These laboratory- and first-trimester-specific GRI for TSH and fT4 shall help in proper diagnosis and treatment of subclinical thyroid dysfunctions. TSH and fT4 MoM values can be used to indicate high or low values in a quantitative manner independent of the reference ranges and may be used by other laboratories.

Total T4 rise in pregnancy: a relook?

Background

Total T4 (TT4) measurement is preferred to free T4 (FT4) especially in last part of pregnancy. Guidelines by American Thyroid Association, European Thyroid Association and Endocrine Society state that TT4 increases 1.5 times pre-pregnant levels after week 16 of pregnancy. However, this is based on a small study conducted 40 years ago which used radioimmunoassay for determination in changes in TT4.

Materials and methods

A cross-sectional study was undertaken to find reference interval for thyroid function in different trimester of pregnancy with special reference to look at the degree of elevation of TT4 as compared to non-pregnant women. Two hundred non-pregnant women (excluding oral contraceptive users) and 600 pregnant women (200 from each trimester) aged 18–40 years were consecutively recruited starting from around 6th week of pregnancy having confirmed singleton pregnancy diagnosed at 8th week by ultrasound. The exclusion criteria included: (1) a personal or family history of thyroid disease; (2) presence of goiter or nodule confirmed by ultrasound; (3) anti-TPO antibody positive state (titre > 35 IU/ml). All subjects were tested for urinary spot iodine concentration and those with UIC < 150 μg/L were excluded. Finally, thyroid function tests (TSH, FT4, TT4, TT3) of 168 non-pregnant women and 163, 153 and 148 women at 1st, 2nd and 3rd trimester respectively were analysed..

Results

Total T4 (mean ± SD, μg/dl) in non pregnant women and in different trimesters was 8.95 ± 1.71, 9.71 ± 2.39, 12.11 ± 1.55, 11.83 ± 1.49 respectively. Rise in TT4 occurred between 10-18th week. The mean TT4 in second trimester increased by 25% as compared with the value at 6-9th week and by 35% as compared to non-pregnant value.

Conclusion

Rise in total T4 in second trimester pregnancy is only around 25% as compared to first trimester value and 35% than the non-pregnant value. Hence multiplying non-pregnant T4 value by 1.5 may actually over-diagnose maternal hypothroxinemia and lead to inappropriate diagnosis and treatment of isolated maternal hypothyroxinemia in a significant proportion of subjects.