Subclinical Hyperthyroidism and Cardiovascular Risk: Recommendations for Treatment

Current Evidence on Prevention of Atrial Fibrillation: Modifiable Risk Factors and the Effects of Risk Factor Intervention

Atrial fibrillation (AF) is one of the most encountered arrhythmias in clinical practice. It is also estimated that the absolute AF burden may increase by greater than 60% by 2050. It is inevitable that AF will become one of the largest epidemics in the world and may pose a major health problem for countries. Although AF rarely causes mortality in the acute period, it causes a significant increase in mortality and morbidity, including a fivefold increase in the risk of stroke, a twofold increase in dementia, and a twofold increase in myocardial infarction in the chronic period. Despite all the advances in the treatment of AF, it is better understood day by day that preventing AF may play a key role in reducing AF and its related complications. Modification of the main modifiable factors such as quitting smoking, abstaining from alcohol, changing eating habits, and exercise seems to be the first step in preventing AF. The strict adherence to the treatment process of secondary causes predisposing to AF such as DM, hypertension, obesity, and sleep apnea is another step in the prevention of AF. Both an individual approach and global public health campaigns can be highly beneficial to reduce the risk of AF. In this review, we aimed to summarize the current evidence on the relationship between modifiable risk factors and AF, and the impact of possible interventions on these factors in preventing or reducing the AF burden in the light of recently published guidelines and studies.

Association of Maternal Hypothyroidism With Cardiovascular Diseases in the Offspring

BACKGROUND

No previous study has examined the effect of maternal hypothyroidism on a broad spectrum of cardiovascular disease (CVD) endpoints in the offspring.

METHODS

A nationwide population-based cohort study based on the linkage of several Danish nationwide registries was conducted to explore whether maternal hypothyroidism is associated with offspring's CVD. Altogether 1,041,448 singletons born between the 1st of January 1978 and the 31st of December 1998 were investigated from the age of 8 years to the 31st of December 2016. Exposure was maternal diagnosis of hypothyroidism across lifespan and the outcome of interest was a CVD diagnosis in the offspring. Cox regression models were performed to estimate the hazard ratios (HRs) of CVD.

RESULTS

Offspring born to mothers with hypothyroidism had an increased risk of CVD (hazard ratios (HR)=1.23, 95% confidence interval (CI): 1.12-1.35), and of several subcategories of CVD including hypertension, arrhythmia, and acute myocardial infarction in offspring. The magnitude of association was the most pronounced in an exposure occur during pregnancy (HR=1.71, 95% CI: 1.10-2.67), which is consistent across all the subgroup analysis, including sibling analysis.

CONCLUSIONS

Maternal hypothyroidism is associated with an increased risk of CVD in offspring. Thyroid hormone insufficiency during pregnancy may predominantly contribute to the observed associations; however, the effects of a shared genetic background and a time-stable familial environment/lifestyle factors cannot be excluded.

Thyroid stimulating hormone testing in ED evaluation of patients with atrial fibrillation and various psychiatric diagnoses

BACKGROUND

Previous studies of thyroid stimulating hormone (TSH) levels in Emergency Department (ED) patients largely have centered on patients with atrial fibrillation (AF). In our ED patients with AF as well as patients with Psychiatric diagnoses (psych) are screened. The purpose of the present study was to compare TSH levels in the 2 groups. Our hypotheses were that an abnormal TSH and/or AF predicted the need for hospital admission and that TSH is more likely decreased in AF and increased in psych patients.

METHODS

Our goal in the study was to compare the use of TSH testing in two ED populations, AF vs. psych patients. The study was a cross sectional cohort of AF vs. psych patients who had TSH levels drawn in the ED over a two year period. Our laboratory ranges were used to determine high vs. low TSH. Two chart examiners collected data after a training process. Charts were reviewed extracting demographic data, TSH levels, outcome (admit vs. discharge), history of AF, thyroid disease, psych diagnoses, presence of CHF, diabetes, hypertension. We compared AF vs. Psych groups using chi square and t-tests for parametric data. Odds ratios were calculated for comparisons between the 2 groups. For non-parametric data Mann Whitney U was used. A logistic regression was performed with the outcome of admission vs. discharge to find predictors of hospital admission. Kappa was calculated for inter-rater agreement. An a priori power analysis showed 80% power with 2 groups of 100 with an absolute difference of 20% between the 2 groups.

RESULTS

252 patients were included, 101 with AF and 152 Psych. Demographics differed in age only with AF patients being older. Mean TSH for AF vs. 2.4 for AF, 2.9 for psych (NS) with no differences in percentages with high or low TSH in the 2 groups. Fifty-three patients had abnormal TSH levels (21%), 27% of AF and 17% of Psych patients (NS). There were significant differences in incidence of CHF, DM, HTN, and tachycardia with more in the AF group (P < 0.001). Significantly more of the psych patients had a history of hypothyroidism (OR 2.28). Our logistic regression showed that taking into account demographics including age, the only predictors of admission were the presence of CHF (aOR 18.6) and having a diagnosis of AF (aOR 4.0).

CONCLUSION

There were no differences in TSH levels between the 2 groups. Twenty-one percent had an abnormal level. CHF and AF predicted hospital admission on regression analysis. Many with these AF or Psych diagnoses had abnormal ED TSH levels that could be useful in diagnosis, maintenance, or continuous treatment for their conditions diagnoses.

Evaluation of endothelial function in exogenous subclinical hyperthyroidism and the effect of treatment

BACKGROUND

Subclinical hyperthyroidism (SHy) is a widespread condition in which cardiovascular manifestations are frequently occur, but there is still a debate about the vascular responsiveness in it. Measuring flow-mediated dilation (FMD) and intimae-media thickness (IMT) are used to evaluate endothelial function in these patients.

MATERIALS AND METHODS

Twenty-five patients with a diagnosis of exogenous SHy and 25 full matched healthy subjects were enrolled. At first FMD of brachial artery and IMT of common carotid artery were obtained from all the participants. In the second phase, in the second phase of study, the dosage of levothyroxine was reduced at least 25% of prior dosage, and this was continued until thyroid stimulating hormone became normal range. Measuring FMD and IMT was repeated after this intervention in the case group.

RESULTS

The mean age of case and control groups were 38.48 ± 12.05 and 36.72 ± 11.15 years, respectively. The mean of FMD in healthy people was dramatically higher than the subclinical hyperthyroid patients (P < 0.001) but no statistically significant difference was found for IMT (P = 0.459). After intervention in the case group, FMD was meaningfully increased (P < 0.001) but IMT of common carotid artery was not considerably changed (P = 0.491).

CONCLUSIONS

This study demonstrated that FMD decreased in exogenous subclinical hyperthyroid patients which could be partially restored by treatment. These findings suggest that treatment of subclinical hyperthyroid state could improve endothelial dysfunction and at the end decreased the cardiovascular complications.

MECHANISMS IN ENDOCRINOLOGY: Impact of isolated TSH levels in and out of normal range on different tissues

Routine treatment of thyroid cancer (TC) includes long-term suppression of TSH. The necessity of this treatment in low- and intermediate-risk patients as well as the extent of TSH suppression is currently under discussion. A literature search was performed to illustrate the role of TSH in extrathyroidal cells and to identify potential reasons for different effects of exogenously suppressed and endogenously low TSH levels. Although adverse effects of subnormal and supranormal TSH blood levels on heart and brain have not been consistently found, studies show a clear negative effect of suppressed TSH levels on bone mineral density. Experimental data also support an important role of TSH in the immune system. The ability of levothyroxine (l-T4) to regulate TSH levels and triiodothyronine levels in a physiological manner is limited. Reduction of circadian changes in TSH levels, decrease of thyroid hormone-binding proteins, prevention of potential compensatory increases of TSH levels (e.g., in old age), and unresponsiveness of TSH-producing cells to TRH on l-T4 treatment might cause adverse effects of suppressed TSH levels. In view of the adverse effects of aggressive TSH suppression, achieving the suggested levels of TSH between 0.9 and 1 mU/l in the treatment of low-to-intermediate risk TC patients appears justified.