Further studies on delineating thyroid-stimulating hormone (TSH) reference range

Gestational thyroid hormone concentrations and risk of attention-deficit hyperactivity disorder in the Norwegian Mother, Father and Child Cohort Study

BACKGROUND

Maternal thyroid function plays an important role in foetal brain development; however, little consensus exists regarding the relationship between normal variability in thyroid hormones and common neurodevelopmental disorders, such as attention-deficit hyperactivity disorder (ADHD).

OBJECTIVE

We sought to examine the association between mid-pregnancy maternal thyroid function and risk of clinically diagnosed ADHD in offspring.

METHODS

We conducted a nested case-control study in the Norwegian Mother, Father and Child Cohort Study. Among children born 2003 or later, we randomly sampled singleton ADHD cases obtained through linkage with the Norwegian Patient Registry (n = 298) and 554 controls. Concentrations of maternal triiodothyronine (T3), thyroxine (T4), T3-Uptake, thyroid-stimulating hormone (TSH) and thyroid peroxidase antibody (TPO-Ab) were measured in maternal plasma, collected at approximately 17 weeks' gestation. Indices of free T4 (FT4i) and free T3 (FT3i) were calculated. We used multivariable adjusted logistic regression to calculate odds ratios and accounted for missing covariate data using multiple imputation. We used restricted cubic splines to assess non-linear trends and provide flexible representations. We examined effect measure modification by dietary iodine and selenium intake. In sensitivity analyses, we excluded women with clinically significant thyroid disorders (n = 73).

RESULTS

High maternal T3 was associated with increased risk of ADHD (5th vs 1st quintile odds ratio  2.27, 95% confidence interval 1.21, 4.26). For FT4i, both the lowest and highest quintiles were associated with an approximate 1.6-fold increase in risk of ADHD, with similar trends found for T4. The FT4i association was modified by dietary iodine intake such that the highest risk strata were confined to the low intake group.

CONCLUSIONS

Both high and low concentrations of maternal thyroid hormones, although within population reference ranges, increase the risk of ADHD in offspring. Increased susceptibility may be found among women with low dietary intake of iodine and selenium.

Pregnancy outcomes and newborn characteristics in women with follicular fluid thyroid autoantibodies undergoing assisted reproduction

Background

Higher levels of thyroid autoantibodies in follicular fluid (FF) of thyroid autoimmunity (TAI) positive women are strongly correlated with serum levels and may have effect on the post-implantation embryo development. Literature highlights that levothyroxine (LT4) treatment may attenuate the risk of adverse pregnancy outcomes. The aim of the study was to estimate the pregnancy and newborn outcomes in women with FF thyroid autoantibodies undergoing assisted reproductive technology (ART).

Methods

The study population included 24 women with confirmed clinical pregnancy, 8 TAI positive and 16 TAI negative women. LT4 supplementation was applied in 20.8% patients, TAI positive.

Results

Pregnancy outcomes were: twin pregnancy rate 41.7%, early miscarriage rate 8.3%, late miscarriage rate 4.2%, preterm birth rate 16.7%, term birth rate 70.8%, live birth rate 96.0%. There was significant difference in serum and in FF TgAbs (p< 0.001)between the groups according to TAI, while serum fT₃ was lower in the group with TAI (p = 0.047). Serum P₄ was higher in LT4 treated group (p = 0.005), with TAI, and newborns in this group had higher birth weight (p = 0.001) and height (p = 0.008). Maternal complications occurred in 23.8% of patients. No congenital malformations in newborns were noted.

Conclusions

Thyroid autoantibodies present in FF may have an effect on the post-implantation embryo development, but have no effect on further course of pregnancy. The special benefit of LT4 treatment for successful ART outcome was demonstrated for newborn anthropometric parameters.

Approach to the Patient: Management and the Long-term Consequences of Graves' Disease in Children

In children, Graves' disease (GD) is the most common cause of hyperthyroidism. Most pediatric patients with GD will not go into lasting remission, even following many years of antidrug therapy. Thus, most pediatric patients will require radioactive iodine (RAI) or surgery. When antithyroid drugs are used, methimazole is the drug of choice. When methimazole is used in children, up to 20% will have minor adverse reactions and serious adverse events occur in up to 1%. RAI is an effective form of therapy when the thyroid size is less than 80 g. Because of concerns of whole-body radiation exposure, it is recommended that RAI be avoided in children under 5 years of age, and dosages less than 10 mCi be used between 5 and 10 years of age. Surgery is an effective treatment in children if performed by a high-volume thyroid surgeon. Because of the scarcity of high-volume pediatric thyroid surgeons, a multidisciplinary approach using pediatric surgeons and endocrine surgeons can be considered. Whereas there is a trend toward long-term antithyroid drug therapy in adults, for several reasons, this approach may not be practical for children. Determining the optimal treatment for the pediatric patient with GD, requires consideration of the risks and benefits relating to age and likelihood of remission.

Reference Intervals for Thyroid-Associated Hormones and the Prevalence of Thyroid Diseases in the Chinese Population

BACKGROUND

Thyroid diseases are highly prevalent worldwide, but their diagnosis remains a challenge. We established reference intervals (RIs) for thyroid-associated hormones and evaluated the prevalence of thyroid diseases in China.

METHODS

After excluding outliers based on the results of ultrasound screening, thyroid antibody tests, and the Tukey method, the medical records of 20,303 euthyroid adults, who visited the Department of Health Care at Peking Union Medical College Hospital from January 2014 to December 2018, were analyzed. Thyroid-associated hormones were measured by the Siemens Advia Centaur XP analyzer. The RIs for thyroid-associated hormones were calculated according to the CLSI C28-A3 guidelines, and were compared with the RIs provided by Siemens. The prevalence of thyroid diseases over the five years was evaluated and compared using the chi-square test.

RESULTS

The RIs for thyroid stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), total thyroxine (TT4), and total triiodothyronine (TT3) were 0.71-4.92 mIU/L, 12.2-20.1 pmol/L, 3.9-6.0 pmol/L, 65.6-135.1 nmol/L, and 1.2-2.2 nmol/L, respectively. The RIs of all hormones except TT4 differed significantly between males and females. The RIs of TSH increased with increasing age. The prevalence of overt hypothyroidism, overt hyperthyroidism, subclinical hypothyroidism, and subclinical hyperthyroidism was 0.5% and 0.8%, 0.2% and 0.6%, 3.8% and 6.1%, and 3.3% and 4.7% in males and females, respectively, which differed from those provided by Siemens.

CONCLUSIONS

Sex-specific RIs were established for thyroid-associated hormones, and the prevalence of thyroid diseases was determined in the Chinese population.

Follicular fluid thyroid autoantibodies, thyrotropin, free thyroxine levels and assisted reproductive technology outcome

OBJECTIVE

Although there are substantial data linking thyroid autoimmunity (TAI) and infertility, data regarding assisted reproductive technology (ART) outcomes and TAI markers in follicular fluid (FF) of women undergoing ART are scarce. Objective of the study was to assess the association of the levels of thyroid autoantibodies in FF and ART outcome expressed as the achieved pregnancies.

METHODS

This study enrolled 52 women undergoing ART (26 TAI positive subjects and 26 age and body mass index matched TAI negative controls). Blood samples were drawn before the initiation of protocol for controlled ovarian stimulation, and thyrotropin (TSH), free triiodothyronine (fT3), free thyroxine (fT4), thyroid peroxidase antibodies (TPOAbs) and thyroglobulin antibodies (TgAbs) levels were measured. TSH, fT4, TPOAbs, TgAbs and progesterone levels were also measured in FF.

RESULTS

There were no significant differences between the groups regarding mean levels of FF TSH and FF fT4. Statistically significant correlation was discovered regarding the levels of serum and FF TPOAbs (0,961, p<0.001 in TAI positive, 0,438, p = 0.025 in TAI negative group) and TgAbs (0,945, p<0.001 in TAI positive, 0,554, p = 0.003 in TAI negative group). Pregnancies rates per initiated cycle and per embryotransfer cycle were significantly different between TAI positive and TAI negative group, (30.8% vs 61.5%), p = 0.026 and (34.8% vs 66.7%), p = 0.029, respectively. Multivariate analysis showed that TAI positive women had less chance to achieve pregnancy (p = 0.004, OR = 0.036, 95% CI 0.004-0.347).

CONCLUSIONS

Higher levels of thyroid autoantibodies in FF of TAI positive women are strongly correlated with serum levels and may have effect on the post-implantation embryo development.

Cognitive functioning and quality of life in patients with Hashimoto thyroiditis on long-term levothyroxine replacement

OBJECTIVE

Intrinsic imperfections of thyroid hormone replacement therapy may affect long-term general well-being. In patients with Hashimoto thyroiditis (HT), cognitive functioning may be affected via altered thyroid hormones action as well as by the autoimmune process. The aim of this study was to evaluate cognitive function and quality of life (QoL) in patients on long-term levothyroxine replacement for HT in relation to thyroid function tests and TPO (thyroid-peroxidase) antibody (TPOAb) status.

DESIGN

Retrospective cross-sectional study.

PATIENTS AND MEASUREMENTS

One-hundred-and thirty patients with HT on long-term levothyroxine replacement and 111 euthyroid control subjects. Both groups were divided into two age subgroups, 20-49 years (N = 59 vs N = 79) and > 50 years (N = 71 vs N = 32). Evaluation included biochemical and neuropsychological tests, evaluating attention, global cognitive status, verbal and working memory, executive function, depression and anxiety, and quality of life. We used ANOVA and partial correlations to test for significant associations.

RESULTS

FT4 (free-thyroxine), FT3 (free-triiodothyronine) levels and FT3/FT4 ratio were not different between patients and controls. Mean TSH (thyroid-stimulating hormone) was normal in all subjects but significantly higher in the patients (20-49 yrs:3.64 ± 2.74 vs 1.93 ± 1.10, >50 yrs:3.93 ± 2.84 vs 1.91 ± 0.90). Antibodies (TgAb,TPOAb) were higher in patients. Global cognitive function (MMSE-Mini mental state examination), conceptual tracking (TMT-Trail Making Test:A/B), verbal divergent thinking (like Phonemic fluency test), and anxiety and depression scores were significantly worse in patients vs controls. QoL was impaired in patients. there was a significant negative correlation between antibodies (TPOAb, TgAb) and quality in life (total SF36 score).

CONCLUSION

Patients on long-term levothyroxine replacement show persistent impairments in both cognitive functioning and general well-being.

TSH cut off point based on depression in hypothyroid patients

BACKGROUND

The prevalence of depressive symptoms in hypothyroidism is high. Considering that hypothyroidism and depression share some clinical features, some researchers use the "brain hypothyroidism" hypothesis to explain the pathogenesis of depression. We aimed to detect a new TSH cut-off value in hypothyroidism based on depression symptoms.

METHODS

A cross-sectional study was conducted on hypothyroid patients referred to endocrine clinics. Individuals who had developed euthyroid state under treatment with levothyroxine with TSH levels of 0.5-5 MIU/L with no need for dosage change were included in the study. After comprehensive history taking, laboratory tests including TSH, T4 and T3 were performed. Beck depression questionnaire was completed for all patients by trained interviewers. TSH cut-off values based on depression was determined by Roc Curve analysis.

RESULTS

The participants were 174 hypothyroid patients (Female; 116: 66.7%, Male; 58: 33.3%) with mean age 45.5 ± 11.7 (19-68) years old. Based on Beck depression test, scores less than 10 was considered healthy and more than 10 were considered depressed. According to Roc curve analysis, the optimal cut- off value of TSH was 2.5 MIU/L with 89.66% sensitivity. The optimal TSH cut- off based on severe depression was 4 MIU/L.

CONCLUSION

The present study suggests that a clinically helpful TSH cut-off value for hypothyroidism should be based on associated symptoms, not just in population studies. Based on the assessment of depression, our study concludes that a TSH cutofff value of 2.5 MIU/L is optimal.