Reference Range Of Thyroid Function Research Articles

Gestational trimester-specific reference ranges for serum thyrotropin and free thyroxine in Japanese.

Thyroid diseases in pregnant and lactating women may result in adverse outcomes for both mothers and infants. A reference range for thyroid function is required in different areas; however, few studies on the gestational change or reference ranges of thyrotropin (TSH) and free thyroxine (FT4) concentrations for Japanese pregnant women have been reported. To establish the gestational trimester-specific reference ranges of serum TSH and FT4 concentrations, our previously published data on 481 pregnant women with the mean age of 30.8 years who provided serum samples as early as gestational week (GW) 6 was compiled by using their percentile values. The overall median urinary iodine concentration (UIC) during pregnancy was 201 μg/L suggesting adequate iodine intake. The prevalence of positive serum thyroid autoantibody (ThAb), i.e., antithyroid peroxidase antibody (TPOAb) and antithyroglobulin antibody (TgAb), was 11.4%. The reference ranges (2.5-97.5th percentile) of serum TSH and FT4 concentration calculated for samples with negative TgAb and TPOAb were 0.04-6.06 mIU/L in the first trimester (T1), 0.31-3.11 mIU/L in the second trimester (T2) and 0.48-3.93 mIU/L in the third trimester (T3) for TSH, and 1.10-1.87 ng/dL (T1), 0.76-1.56 ng/dL (T2) and 0.76-1.14 ng/dL (T3) for FT4. Compared to published data around the world in the 2017 American Thyroid Association (ATA) guideline, both the upper and lower limits of our TSH and FT4 reference ranges in the first trimester were higher than those in other countries. Further research is necessary in larger samples.

Normal Reference Range for Serum TSH, Free T4, Total T4, and Total T3 on Roche® Platforms in Basrah, Iraq

Background: Thyroid function tests are mandatory in clinical practice because symptoms and signs are not reliable to discriminate between various types of thyroid disease.
 Aim: The aim of this study was to determine assay-specific reference range for serum free T4, total T4, total T3 and TSH among healthy non-pregnant adult cohort for Roche® platforms in Basrah (Southern Iraq) from single laboratory in a tertiary center using indirect approach of the available data.
 Methods: A Cross sectional study for non-pregnant adults 19 years and above. Sera were analyzed by using cobs e411 for thyroid functions tests.
 Results: Total enrolled persons were 10,078. The 95% reference intervals for TSH were 0.20-6.50 μIU/mL, which increased with age though not linear, for free T4 were 0.8-1.70 ng/dL, for total T4 were 3.78-15.33 μg/dL, and for total T3 were 0.80-2.50 ng/mL.
 Colcusion: Cobs e411(Roche® analytical platform) analyzer reference range for thyroid function cannot be applied for Iraqi population .

Thyroid Function and Physical Activity: A Population-Based Cohort Study.

Background: Thyroid hormones are important metabolic regulators exerting effects in multiple systemic functions including muscular and cardiorespiratory function. Thyroid hormones may influence physical activity levels. However, there are currently no studies evaluating the association between thyroid function and physical activity levels in the general population. Methods: In a population-based cohort study between 2006 and 2013, we assessed the cross-sectional and longitudinal (with a mean follow-up time of 5 years) association of serum thyrotropin (TSH) and free thyroxine (fT4) with physical activity (metabolic equivalent task [MET] hours per week). Information on physical activity was collected using a validated questionnaire (Longitudinal Aging Study Amsterdam, median 22.50 MET hours per week). The association of TSH and fT4 with physical activity was examined using linear regression models in the cross-sectional and longitudinal analyses, adjusted for age, sex, lifestyle factors, and cardiovascular disease. In sensitivity analyses, we examined the association between thyroid function and physical activity including only participants within the reference range of thyroid function. We additionally examined moderate and vigorous physical activity separately as outcomes. Results: We included 2470 participants for the cross-sectional analysis (mean age 57.3 years, 58% women) and 1907 participants for the longitudinal analysis (mean age 56.9 years). There was no association between TSH (mIU/L) or fT4 (ng/dL) and physical activity (β = 0.65, 95% confidence interval [CI, -1.67 to 2.98] and β = 2.76, [CI -7.15 to 12.66], respectively) on cross-sectional analysis. Similarly, in the longitudinal analyses, we observed no association of TSH (β = 1.16, [CI -1.31 to 3.63]) or fT4 (β = -6.63, [CI -17.06 to 3.80]) with physical activity. Conclusions: We did not observe an association between the endogenous thyroid hormone level and total physical activity. Further studies need to be performed to evaluate whether thyroid hormone replacement therapy is associated with physical activity.

P3414Differences in total life expectancy and life expectancy with and without non-communicable diseases within the reference range of thyroid function

Abstract Background Variations in thyroid function within the reference ranges are associated with an increased risk of diseases and death. However, the impact of thyroid function on life expectancy (LE) and the number of years lived with and without non-communicable diseases (NCD) remains unknown. Purpose We aimed to investigate the association of thyroid function with total LE and LE with and without NCD among euthyroid subjects. Methods Participants of the Rotterdam Study without known thyroid disease and with thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels within the reference ranges were eligible. NCD were defined as the presence of cardiovascular disease, diabetes mellitus type 2, or cancer. We used multistate life tables to calculate the total LE and LE with and without NCD among TSH and FT4 tertiles, in men and women. LE estimates were obtained using prevalence, incidence rates and hazard ratios for three transitions (healthy to NCD, healthy to death and NCD to death). Analyses were adjusted for sociodemographic and cardiovascular risk factors. Results The mean (standard deviation) age of 7644 participants was 64.5 (9.7) years and 52.2% were women. Over a median follow-up of 8 years, we observed 1396 incident NCD events and 1422 deaths. Compared with those in the lowest tertile, men and women in the highest TSH tertile lived 1.5 (95% confidence interval [CI], 0.8; 2.3) and 1.5 (95% CI, 0.8; 2.2) years longer, respectively; of which 1.4 (95% CI, 0.5; 2.3) and 1.3 (95% CI, 0.3; 2.1) years with NCD. Compared with those in the lowest tertile, the difference in LE for men and women in the highest FT4 tertile was −3.7 (95% CI, −5.1 to −2.2) and −3.3 (95% CI, −4.7; −1.9), respectively; of which −1.8 (95% CI, −3.1 to −0.7) and −2.0 (95% CI, −3.4 to −0.7) years without NCD. Life expectancy in TSH and FT4 tertiles Conclusions There are meaningful differences in total LE, LE with and without NCD within the reference ranges of thyroid function. People with low-normal thyroid function live more years with and without NCD than those with high-normal thyroid function. These findings support a reevaluation of the current reference ranges of thyroid function.

Trimester-specific reference ranges for thyroid hormones in pregnant women.

The aim of this study was to determine the trimester-specific reference range of thyroid function in Nanjing.A total of 805 pregnant women in the 1st, 2nd, and 3rd trimesters were recruited in the prospective, observational study during their routine antenatal clinic visit and 282 nonpregnant subjects served as controls. A questionnaire was completed by the subjects to record their personal health history, family history of thyroid disease, and consumption of estrogen or antithyroid drugs. Thyroid palpation was performed to exclude the thyroid goiter. Thyroid function and urine iodine were measured by chemiluminescence and arsenic cerium analysis.The trimester-specific reference ranges in Nanjing were as follows: thyroid-stimulating hormone (TSH) 0.02 to 3.78 mIU/L, free thyroxine (FT4) 13.93 to 26.49 pmol/L, total thyroxine (TT4) 103.39 to 319.43 nmol/L in the 1st trimester. TSH 0.47 to 3.89 mIU/L, FT4 12.33 to 19.33 pmol/L, TT4 92.28 to 234.88 nmol/L in the 2nd trimester. TSH 0.55 to 4.91 mIU/L, FT4 11.38 to 19.21 pmol/L, TT4 83.54 to 258.12 nmol/L in the 3rd trimester. According to the TSH reference range recommended by American Thyroid Association (ATA), the prevalence of subclinical hypothyroidism, subclinical hyperthyroidism, hyperthyroidism, hypothyroxinemia, and thyroid peroxidase antibody-positive were 12.42%, 0.50%, 0.99%, 1.61%, and 11.80%, respectively, prevalence according to the trimester-specific reference range were 1.99%, 0.25%, 1.61%, 0.37%, and 1.61%, respectively, which showed elevated hypothyroxinemia incidence and declined incidence of subclinical hypothyroidism and hyperthyroidism.Trimester-specific reference range varied from that of ATA's recommendation, influencing the diagnosis, and treatment of pregnant thyroid disorders. To detect and control these disorders properly, setting up trimester-specific reference is clinically essential.

Thyroid function and risk of type 2 diabetes: a population-based prospective cohort study.

BackgroundThe association of thyroid function with risk of type 2 diabetes remains elusive. We aimed to investigate the association of thyroid function with incident diabetes and progression from prediabetes to diabetes in a population-based prospective cohort study.MethodsWe included 8452 participants (mean age 65 years) with thyroid function measurement, defined by thyroid-stimulating hormone (TSH) and free thyroxine (FT4), and longitudinal assessment of diabetes incidence. Cox-models were used to investigate the association of TSH and FT4 with diabetes and progression from prediabetes to diabetes. Multivariable models were adjusted for age, sex, high-density lipoprotein cholesterol, and glucose at baseline, amongst others.ResultsDuring a mean follow-up of 7.9 years, 798 diabetes cases occurred. Higher TSH levels were associated with a higher diabetes risk (hazard ratio [HR] 1.13; 95 % confidence interval [CI], 1.08–1.18, per logTSH), even within the reference range of thyroid function (HR 1.24; 95 % CI, 1.06–1.45). Higher FT4 levels were associated with a lower diabetes risk amongst all participants (HR 0.96; 95 % CI, 0.93–0.99, per 1 pmol/L) and in participants within the reference range of thyroid function (HR 0.96; 95 % CI, 0.92–0.99). The risk of progression from prediabetes to diabetes was higher with low-normal thyroid function (HR 1.32; 95 % CI, 1.06–1.64 for TSH and HR 0.91; 95 % CI, 0.86–0.97 for FT4). Absolute risk of developing diabetes type 2 in participants with prediabetes decreased from 35 % to almost 15 % with higher FT4 levels within the normal range.ConclusionsLow and low-normal thyroid function are risk factors for incident diabetes, especially in individuals with prediabetes. Future studies should investigate whether screening for and treatment of (subclinical) hypothyroidism is beneficial in subjects at risk of developing diabetes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12916-016-0693-4) contains supplementary material, which is available to authorized users.

Effect of Thyroid Function Variations Within the Laboratory Reference Range on Health Status, Mood, and Cognition in Levothyroxine-Treated Subjects.

There has been recent debate within the thyroid field regarding whether current upper limits of the thyrotropin (TSH) reference range should be lowered. This debate can be better informed by investigation of whether variations in thyroid function within the reference range have clinical effects. One important target organ for thyroid hormone is the brain, but little is known about variations in neurocognitive measures within the reference range for thyroid function. This was a cross-sectional study of 132 otherwise healthy hypothyroid subjects receiving chronic replacement therapy with levothyroxine (LT4) who had TSH levels across the full span of the laboratory reference range (0.34-5.6 mU/L). Subjects underwent detailed tests of health status, mood, and cognitive function, with an emphasis on memory and executive functions. Subjects with low-normal (≤2.5 mU/L) and high-normal (>2.5 mU/L) TSH levels did not differ on most tests of health status, mood, or cognitive function, and there were no correlations between TSH, free T4, or free T3 levels and most outcomes. There was, however, a suggestion that thyroid function affected performance on the Iowa Gambling Task, which mimics real life decision-making. Subjects with low-normal TSH levels made more advantageous decisions than those with high-normal TSH levels. Variations in thyroid function within the laboratory reference range do not appear to have clinically relevant effects on health status, mood, or memory in LT4 treated subjects. However, decision making, which encompasses many executive functions, may be affected. Unless further studies strengthen this finding, these data do not support narrowing the TSH reference range.

Reference range of thyroid function (FT3, FT4 and TSH) among Indian adults

ObjectivesTo generate thyroid hormone reference norms using electro-chemiluminescence technique. Design and methodsCross sectional study on apparently normal 4349 Delhi adults (18–86years). Predetermined exclusion criteria (goiter, hypoechogenicity or nodularity on ultrasound, elevated anti-thyroid peroxidase antibody, hypo or hyperthyroidism and family history of thyroid dysfunction) excluded 2433 subjects leaving 1916 (916 males and 1000 females) as the reference population. ResultsMean age and BMI of the reference population were 41.2±18.1years and 24.5±4.4kg/m2 respectively. Median urinary iodine excretion was 233.6μg/L (79–458;3rd–97th centile). The population was categorized into various age groups (18–30, 31–40, 41–50, 51–60, 61–70 and ≥70years). Overall FT3 and FT4 values in the reference population irrespective of age, ranged from 2.4–8.8 (mean 4.6±0.9) pmol/L and 10.1–24.8 (mean 15.40±2.0) pmol/L, respectively. Mean TSH value in the reference population was 2.2±0.9mIU/L which was significantly lower than that of total population (3.8±6.1; p<0.001). ConclusionFT3 values were observed to be significantly higher in men than women (p=0.001). The centiles (3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th and 97th) of FT3, FT4 and TSH were derived for reference purposes in Indian adults. This community based study in Indian adults has established mean reference intervals for FT3, FT4 and TSH for different age groups for both sexes separately using strict exclusion criteria. These can be used as reference norms for Indian adults.

Narrow intra-individual variation of maternal thyroid function in pregnancy based on a longitudinal study on 132 women

Adaptive alterations in maternal physiology cause changes in thyroid hormone levels throughout pregnancy, and precise biochemical evaluation is thus highly dependent on gestation-specific reference intervals and expected intra-individual variation. The aim of the study was the assessment of the intra-individual variation as well as the longitudinal course of thyroid hormones during normal pregnancy and factors that influence the normal reference range for thyroid function. For this purpose, a longitudinal statistical model was applied. In a cohort of 132 pregnant women, serial blood samples were obtained and ultrasound scans were performed throughout pregnancy. Serum levels of TSH, free and total thyroxine (T(4)), free and total triiodothyronine (T(3)) as well as autoantibodies against thyroid peroxidase and thyroglobulin were measured in 979 serum samples. Intra-individual variations of thyroid hormone concentrations were smaller than inter-individual variations (individuality index range: 0.38-0.71). Maternal height was positively associated with free T(4) (FT(4)) (b=0.003; P=0.031) and pre-pregnancy body mass index with T(3) and free T(3) (b=0.017; <0.001 and b=0.007; P<0.001). Smoking was positively associated with T(4) and FT(4), but it was modulated by gestational age. Gestation-specific reference intervals for thyroid function variables from autoantibody-negative participants are presented. In accordance with the data from nonpregnant adults, intra-individual variations of thyroid hormones were smaller than inter-individual variations also during pregnancy. In the evaluation of thyroid function in pregnancy, the individual longitudinal course of thyroid hormones rather than absolute values should be considered. We present a longitudinal model for the prediction of maternal thyroid function tests in pregnant women.