TSH Levels in Subclinical Hypothyroidism in the 97.5th Percentile of the Population

Estimation of left ventricular functions in patients with subclinical hypothyroidism: a meta-analysis

Objective

To evaluate left ventricular (LV) function in patients with subclinical hypothyroidism (ScH) compared to healthy individuals and to provide clinical hints for practitioners.

Methods

PubMed, Embase, Cochrane Library, and Web of Science were systematically searched in this meta-analysis. Studies evaluating LV function in ScH patients were included. Standardized mean difference (SMD) and the 95% confidence intervals (CIs) were calculated as effect size. Heterogeneity and risks of bias of included studies were assessed.

Results

A total of 9 studies were identified as eligible. The SMD for fractional shortening (FS, %) was -0.21 (95% CI: -0.60, 0.17; z = -1.08, p = 0.2788). The pooled SMD for systemic vascular resistance (SVR, dynes/sec·cm-5) was -0.41 (95% CI: -1.31, 0.49; z = -0.89, p = 0.3744). The pooled SMD for early diastolic mitral flow velocity/late diastolic mitral flow velocity (E/A) ratio was -0.74 (95% CI: -1.09, -0.39; z = -4.13, p < 0.001). The pooled SMD for ejection fraction (EF, %) was -0.35 (95% CI: -0.59, -0.12; z = -2.95, p = 0.0032).

Conclusion

ScH patients had significantly worse LV function parameters than healthy controls. These changes in LV function may be involved in the management of ScH.

Association of high BMI with subclinical hypothyroidism in young, first-episode and drug-naïve patients with major depressive disorder: a large-scale cross-sectional study

Thyroid dysfunction is known to be associated with obesity, but the reliability of this relationship is easily affected by drug treatment, age, and subclinical hypothyroidism (SCH) with no apparent symptoms. Our research aims to compare obese and overweight BMI ranges with SCH and without SCH in a large sample of young, first-episode and drug-naïve (FEDN) patients with major depressive disorder (MDD), which has received little systemic investigation. A total of 1289 FEDN MDD young outpatients were recruited for this study. Serum thyroid function and lipid level parameters were measured; HAMD and PANSS scales were used to assess patients' depression and positive symptoms. A self-administered questionnaire collected other clinical and demographic data. The prevalence of SCH in FEDN MDD young patients was 58.26%. Compared to patients without SCH, the patients with SCH had a more prolonged illness duration, higher BMI levels, increased prevalence of overweight and obesity, higher HAMD score and PANSS-positive symptom scores, higher levels of TG, TC, LDL-C, and lower levels of HDL-C. Further logistic regression indicated that overweight BMI, obese BMI, illness duration, HAMD score, HDL-C, and TC were significantly associated with SCH. Our results indicate that obesity and overweight may be associated with SCH in young, FEDN MDD patients. The importance of regular thyroid function assessment in young FEDN MDD patients with high BMI should be taken into account.

Increase in Thyrotropin Is Associated with an Increase in Serum Prolactin in Euthyroid Subjects and Patients with Subclinical Hypothyroidism

Background: Prevalence and clinical significance of hyperprolactinemia in subclinical hypothyroidism have been reported in few studies. The upper limit of the normal range for TSH used to diagnose subclinical hypothyroidism is a matter of controversy. Some experts believe that the upper limit of the normal TSH range should be reduced from 4.2 to 2.5 mIU/L. Some evidence suggests a positive relationship between TSH > 2.5 mIU/L and cortisol as an indicator of metabolic stress. With this view prolactin as a stress hormone can be elevated in TSH >2.5 in comparison to TSH< 2.5. Hence the aim of this study was to evaluate the relationship between TSH and prolactin levels in the TSH range <10.

Methods: This cross-sectional study was performed on apparently healthy subjects with TSH<10 mIU/L. Subjects with the age of 18 to 35 years were enrolled. The sera were analyzed for prolactin, FT3, FT4, TSH, TPO-Ab and Tg-Ab.

Results: From the total number of 519 participants, in 65 subjects (12.5%) TSH was < 2.5. Seventy-nine subjects (15.2%) had TSH: 2.5-4.2 and 375 (72.3%) of the participants had TSH> 4.2 mIU/L. The mean age, weight and BMI of subjects in the three TSH groups were not significantly different. In the three TSH groups, the prevalence of hyperprolactinemia was zero, 3.8 and 30.7%, respectively. There was a positive and significant correlation between prolactin and TSH levels (r=0.613).

Conclusion: Hyperprolactinemia is common in patients with subclinical hypothyroidism (30.7%) and there is a positive correlation between TSH and PRL in subjects with TSH<10 mIU/l.

Subclinical hypothyroidism in women's health: from pre- to post-menopause

OBJECTIVE

Subclinical hypothyroidism (SCH) is a quite frequent condition among women, affecting 3-12% of the general population. Its consequences on women's health in reproductive age, pregnancy and menopause have been extensively investigated but data about the effective impact of treatment with levothyroxine (LT4) remain conflicting.

METHODS

This is a narrative review and analysis of the most relevant data until June 2021.

RESULTS

SCH may affect reproduction. Evidence suggests that women with SCH undergoing assisted reproductive technique (ART) may benefit from LT4 therapy whereas there are no conclusive data regarding women attempting natural conception. SCH may be associated with several negative pregnancy outcomes, that is to say recurrent pregnancy loss (RPL), preterm delivery, preeclampsia and neurocognitive disturbances of offspring. However, the protective role of LT4 treatment has been established in selected cases, for instance in thyroid peroxidase antibody (TPOAb) -positive women with TSH greater than the pregnancy specific reference range and/or in TPOAb-negative women with TSH >10.0 mIU/L. In menopause, SCH can worsen the negative cardio-metabolic effects of hormonal loss and/or aging, by exacerbating dyslipidaemia and hypertension. Nevertheless, robust data about the benefits of LT4 therapy are still lacking and treatment should be encouraged with caution.

CONCLUSIONS

SCH represents a challenging condition during pre- and post- menopause. An aware knowledge of its possible principal consequences could help all clinicians who are involved in women's health to manage more properly it, preventing its sequelae.

Prognostic Value of Normal Thyroid Stimulating Hormone in Long-Term Mortality in Patients With STEMI

BACKGROUND

Although within the normal range, thyroid stimulating hormone (TSH) levels are associated with cardio-metabolic disorders and have an effect on the cardiovascular system. The aim of our study was to assess the prognostic value of normal TSH on long-term mortality in patients with ST-segment elevation myocardial infarction (STEMI).

METHODS

Consecutive STEMI patients who had a TSH level within the normal range (0.55-4.78 μIU/ml) were enrolled from November 2013 to December 2018. Patients were stratified into three groups depending on the tertile of TSH level, and all-cause mortality and cardiac death were compared. TSH concentrations associated with risk of all-cause mortality were evaluated in a continuous scale (restricted cubic splines) and the Cox proportional hazards regression model.

RESULTS

A total of 1,203 patients with STEMI were eligible for analysis. During a median follow-up of 39 months, patients in the 3rd tertile group had higher all-cause mortality (20.1% vs. 12.2% and 14.3%, p = 0.006) and cardiac death (15.4% vs. 7.7% and 12.3%, p = 0.001) as compared to the 1st and 2nd tertile groups. The Cox proportional hazards model showed that TSH was an independent predictor on long-term all-cause mortality (HR: 1.248, 95% CI: 1.046-1.490, p = 0.014). However, subgroup analysis indicated that TSH (HR: 1.313, 95% CI: 1.063-1.623, p = 0.012) was only significantly associated with long-term all-cause mortality in the patients without emergency reperfusion therapy. Restricted cubic spline analyses showed a linear relationship between TSH concentrations and all-cause mortality (P for non-linearity = 0.659).

CONCLUSIONS

A Higher TSH level - even in a normal range is associated with long-term mortality in patients with STEMI, proposing an additional indication to identify STEMI patients with poor prognosis.

Comparison of Five Different Criteria for Diagnosis of Subclinical Hypothyroidism in a Large-Scale Chinese Population

BACKGROUND

Several different criteria for subclinical hypothyroidism (SCH) have been used in the literature, but the performance of these criteria was unknown.

OBJECTIVE

This retrospective study was to evaluate the diagnostic criteria for SCH.

METHODS

Eligible participants were based on centration of thyroglobulin antibodies (TG-Ab), thyroid peroxidase antibodies (TPO-Ab), and five thyroid-related hormones including total thyroxine (TT4), total triiodothyronine (TT3), free thyroxine (FT4), free triiodothyronine (FT3), and thyroid-stimulating hormone (TSH). Euthyroid individuals were identified via specific criteria. Five different SCH diagnostic criteria were compared based on the distributions of those indicators. An appropriate TSH cut-off value was reconsidered.

RESULTS

The study included 145,015 participants. The number of SCH cases diagnosed using criterion 5 was significantly different compared to the cases diagnosed using criteria 1-4 (P<0.05) and had the highest positive proportions of TG-Ab and TPO-Ab. Analysis of 60,515 subjects with normal other thyroid hormones revealed a median TSH concentration of 2.04 mIU/L, and the P _2.5-P _97.5 CI was 0.48-7.03 mIU/L. When the threshold for TSH elevation was elevated from ≥4.5 mIU/L to ≥6.50 mIU/L, the number of diagnosed SCH cases decreased from 7.30% to 2.09% and the proportions of positive TG-Ab and TPO-Ab increased from 23.69% and 24.07% to 33.75% and 35.06%, respectively (P<0.01).

CONCLUSIONS

Combination of an elevated TSH and normal TT3, TT4, FT3, and FT4 concentrations is a must for the diagnosis of SCH. A new TSH threshold should be identified for better patient monitoring and management, according to the real-world characteristics of TSH distribution in Chinese population.

Subclinical Hypothyroidism: Prevalence, Health Impact, and Treatment Landscape

Subclinical hypothyroidism (sHypo) is defined as normal serum free thyroid hormone levels coexisting with elevated serum thyroid-stimulating hormone (TSH) levels. sHypo is a common condition observed in clinical practice with several unique features. Its diagnosis should be based on an understanding of geographic and demographic differences in biochemical criteria versus a global reference range for TSH that is based on the 95% confidence interval of a healthy population. During the differential diagnosis, it is important to remember that a considerable proportion of sHypo cases are transient and reversible in nature; the focus is better placed on persistent or progressive forms, which mainly result from chronic autoimmune thyroiditis. Despite significant evidence documenting the health impacts of sHypo, the effects of levothyroxine treatment (LT4-Tx) in patients with sHypo remains controversial, especially in patients with grade 1 sHypo and older adults. Existing evidence suggests that it is reasonable to refrain from immediate LT4-Tx in most patients if they are closely monitored, except in women who are pregnant or in progressive cases. Future research is needed to further characterize the risks and benefits of LT4-Tx in different patient cohorts.