Challenges in the Management of Atrial Fibrillation With Subclinical Hyperthyroidism

The Impact of Physical Activity on Thyroid Health: Insights From Representative Data in Korea

CONTEXT

Thyroid hormones are essential for energy metabolism related to thermogenesis and oxygen consumption.

OBJECTIVE

This study evaluated the potential association of thyroid function including thyroid peroxidase antibodies (TPOAb) with physical activity in nationally representative data.

DESIGN/SETTING/PARTICIPANTS

This retrospective cohort study used data from the Korean National Health and Nutrition Examination Survey between 2013 and 2015. Physical activity (PA) was assessed using metabolic equivalents based on the validated Korean version of the International Physical Activity Questionnaire Short Form. PA level was categorized into 3 groups of high, moderate, and low. Participants with abnormal thyroid function test, restricted activity, or previous history of thyroid disease were excluded in the study.

RESULTS

A total of 5372 participants was finally selected. The free T4 level was lowest in the low PA group, while TSH was not significantly different among the groups. TPOAb titers increased in the following order: moderate PA, low PA, and high PA. After adjustment for confounding factors, moderate PA was associated with a high T4 level and a decrease in TSH and TPOAb with significance. However, there were no significant changes in free T4, TSH, or TPOAb titer in the high PA group. In a subanalysis, females with moderate PA showed a significant decrease in TSH and TPOAb. In both males and females, insulin sensitivity was increased with moderate PA. In obese participants, TSH negatively correlated with PA, and free T4 levels decreased in the low PA. The sensitivity to thyroid hormone did not differ in our study.

CONCLUSION

The present study found an association between thyroid function and moderate PA. Therefore, moderate-intensity PA should be recommended to improve thyroid function.

Epidemiology, prognosis, and challenges in the management of hyperthyroidism-related atrial fibrillation

Atrial fibrillation (AF) is a common condition with a global estimated prevalence of 60 million cases, and the most common cardiac complication of hyperthyroidism, occurring in 5-15% of overtly hyperthyroid patients. Additionally, subclinical hyperthyroidism and high-normal free T4 have been associated with an increased risk in the development of AF. Hyperthyroidism-related AF is a reversible cause of AF, and the majority of patients spontaneously revert to sinus rhythm in 4-6 months during or after restoration of euthyroidism. Therefore, restoring thyroid function is an indispensable element in hyperthyroidism-related AF management. Rate control with beta-blockers consists another first-line therapy, reserving rhythm control in cases of persistent hyperthyroidism-related AF. It is still controversial whether hyperthyroidism is an independent risk factor of stroke in nonvalvular AF. As a result, initiating anticoagulation should be guided by the clinical thromboembolic risk score CHA2DS2-VASc score in the same way it is applied in patients with non-hyperthyroidism-related AF. Treatment with the novel direct oral anticoagulants appears to be as beneficial and may be safer than warfarin in patients with hyperthyroidism-related AF. In this review, we address the epidemiology, prognosis, and diagnosis of hyperthyroidism-related AF, and we discuss the management strategies and controversies in patients with hyperthyroidism-related AF.

Prognostic implications of thyroid disease in patients with atrial fibrillation

Atrial fibrillation (AF) is often accompanied by thyroid disease (THD). This study aimed to explore the relationship between THD and the occurrence of significant clinical outcomes in patients with AF. This post hoc analysis utilized data from the MISOAC-AF trial (NCT02941978), which enrolled hospitalized patients with AF. Patients were categorized based on their THD history into hyperthyroidism, hypothyroidism, or euthyroidism. Cox regression models were employed to calculate unadjusted and adjusted hazard ratios (aHRs). The primary outcomes of interest included all-cause mortality, cardiovascular death, and hospitalizations during the follow-up period. The study included 496 AF patients (mean age 73.09 ± 11.10 years) with available THD data, who were followed-up for a median duration of 31 months. Among them, 16 patients (3.2%) had hyperthyroidism, 141 (28.4%) had hypothyroidism, and 339 (68.4%) had no thyroid disease. Patients with hypothyroidism exhibited higher rates of hospitalization during follow-up (aHR: 1.57, 95% CI 1.12 to 2.20, p = 0.025) compared to the euthyroid group. Elevated levels of thyroid-stimulating hormone (TSH) were correlated with an increased risk of cardiovascular mortality (aHR: 1.03, 95% CI 1.01 to 1.05, p = 0.007) and hospitalizations (aHR: 1.06, 95% CI 1.01 to 1.12, p = 0.03). Conversely, lower levels of triiodothyronine (T3) were associated with higher risks of all-cause mortality (aHR: 0.51, 95% CI 0.31 to 0.82, p = 0.006) and cardiovascular mortality (aHR: 0.42, 95% CI 0.23 to 0.77, p = 0.005). Among patients with AF, hypothyroidism was associated with increased hospitalizations. Furthermore, elevated TSH levels and decreased T3 levels were linked to higher cardiovascular and all-cause mortality risks, respectively.

Analysis of Subclinical Thyroid Dysfunction and Metabolic Abnormality in 28568 Healthy People

We analyzed the detection rates of metabolic syndrome (MetS) and subclinical thyroid dysfunction, including subclinical hyperthyroidism (SCHyper) and subclinical hypothyroidism (SCH), in healthy people, as well as their relationship. Clinical data were collected from 28,568 healthy individuals who underwent physical examinations. The detection rates of SCHyper, SCH, and MetS, as well as in different genders and ages, were analyzed. The detection rate of SCHyper and SCH in females was significantly higher than that in males (P < 0.001), but that of MetS in males was significantly higher than that in females (P < 0.001). In each age group, the detection rate of SCH in females was higher than that in males (P < 0.001). The detection rate of SCH was significantly different in different age groups (P < 0.001). The detection rates of hyperlipidemia (P < 0.001), obesity (P = 0.004), hypertension (P = 0.009), and hyperglycemia (P < 0.001) in the female SCH group were significantly higher than those in the normal group. The detection rates of hyperlipidemia (P = 0.006), obesity (P = 0.04), and hypertension (P = 0.04) in the male SCH group were higher than those in the normal group. The males with SCHyper were more prone to hyperlipidemia (P = 0.02) and obesity (P = 0.03). In addition, the female SCHyper group was not significantly different from the normal group (P > 0.05). Conclusively, the detection rate of SCHyper and SCH in females is higher than that in males, which increases with age. Attention should be paid to subclinical thyroid dysfunction in elderly people, especially females. Early individualized screening and early intervention should be carried out for people with abnormal metabolism.

Update on subclinical thyroid dysfunction

Subclinical thyroid dysfunction is defined by serum thyroid-stimulating hormone (TSH) levels either greater or less than the reference range with normal thyroxine (T4) concentrations, and consists of subclinical hypothyroidism (SCH) and subclinical hyperthyroidism (SCHyper). For the proper diagnosis of SCH, it is most important to be able to correctly evaluate the serum TSH levels, which have numerous unique characteristics. We also need to be versed in TSH harmonization, which was recently launched world-wide. In this review, we will attempt to determine the best clinical approaches to the treatment of subclinical thyroid dysfunction based on recent guidelines published from several countries and novel findings of several recent large-scale clinical studies.

Postischemic Neuroprotection of Aminoethoxydiphenyl Borate Associates Shortening of Peri-Infarct Depolarizations

Brain stroke is a highly prevalent pathology and a main cause of disability among older adults. If not promptly treated with recanalization therapies, primary and secondary mechanisms of injury contribute to an increase in the lesion, enhancing neurological deficits. Targeting excitotoxicity and oxidative stress are very promising approaches, but only a few compounds have reached the clinic with relatively good positive outcomes. The exploration of novel targets might overcome the lack of clinical translation of previous efficient preclinical neuroprotective treatments. In this study, we examined the neuroprotective properties of 2-aminoethoxydiphenyl borate (2-APB), a molecule that interferes with intracellular calcium dynamics by the antagonization of several channels and receptors. In a permanent model of cerebral ischemia, we showed that 2-APB reduces the extent of the damage and preserves the functionality of the cortical territory, as evaluated by somatosensory evoked potentials (SSEPs). While in this permanent ischemia model, the neuroprotective effect exerted by the antioxidant scavenger cholesteronitrone F2 was associated with a reduction in reactive oxygen species (ROS) and better neuronal survival in the penumbra, 2-APB did not modify the inflammatory response or decrease the content of ROS and was mostly associated with a shortening of peri-infarct depolarizations, which translated into better cerebral blood perfusion in the penumbra. Our study highlights the potential of 2-APB to target spreading depolarization events and their associated inverse hemodynamic changes, which mainly contribute to extension of the area of lesion in cerebrovascular pathologies.