Pulmonary hypertension and Hashimoto's thyroiditis: does a relationship exist?

The Role of Regulatory T Cells in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a chronic, incurable condition characterized by pulmonary vascular remodeling, perivascular inflammation, and right heart failure. Regulatory T cells (Tregs) stave off autoimmunity, and there is increasing evidence for their compromised activity in the inflammatory milieu of PAH. Abnormal Treg function is strongly correlated with a predisposition to PAH in animals and patients. Athymic Treg-depleted rats treated with SU5416, an agent causing pulmonary vascular injury, develop PAH, which is prevented by infusing missing CD4⁺CD25^highFOXP3⁺ Tregs. Abnormal Treg activity may also explain why PAH disproportionately affects women more than men. This mini review focuses on the role of Tregs in PAH with a special view to sexual dimorphism and the future promise of Treg therapy.

Serum-Free Thyroxine Levels Were Associated with Pulmonary Hypertension and Pulmonary Artery Systolic Pressure in Euthyroid Patients with Coronary Artery Disease

The aim of this study was to evaluate the association between thyroid hormone levels, pulmonary hypertension (PH), and pulmonary artery systolic pressure (PASP) in euthyroid patients with coronary artery disease (CAD). A cross-sectional study was conducted in individuals who underwent coronary angiography and were diagnosed as CAD from March 2013 to November 2013. 811 subjects (185 women and 626 men) were included in this study. PASP was measured by transthoracic Doppler echocardiography. 86 patients were diagnosed as PH and had significantly higher free thyroxine (FT₄) levels than those without PH. Multiple logistic regression analysis demonstrated an independent association of FT₄ levels with PH after adjustment of gender, age, body mass index, systolic blood pressure, left ventricular ejection fraction, hypertension, and medication use of calcium channel blockers, ACE inhibitors, angiotensin II receptor antagonists, and nitrates. Serum-free triiodothyronine (FT₃) and thyroid-stimulating hormone (TSH) were not associated with PH. Furthermore, multivariate linear regression analysis showed that FT₄ levels emerged as an independent predictor for PASP, while FT₃ and TSH levels were not associated with PASP. Our study demonstrated that, in euthyroid patients with CAD, FT₄ was an independent risk factor for PH, and FT₄ levels were independently associated with PASP.

Pulmonary hypertension in thyroid diseases

The influence of thyroid hormones on cardiovascular system is well established. Thyroid diseases can effectively enhance the alteration on cardiovascular system by influencing chronotropic and inotropic actions of the heart; altering the strength and the speed of contraction, the speed of relaxation, the duration of the potential of action, and the duration of the refractory period and atrio-ventricular conduction time; modulating circulation and peripheral vascular beds. One of the more intriguing insights in the connection between thyroid diseases and cardiovascular alterations is related to the evaluation of the influence of thyroid hormones on pulmonary vascular beds. Literature reported several studies regarding the association between both hypothyroidism and hyperthyroidism and the occurrence of increased vascular pulmonary arterial pressure. Nevertheless, the pathogenetic mechanisms able to explain such relationship are not fully understood. Many doubts still persist in the comprehension of the mechanisms of pulmonary hypertension in thyroid diseases. The aim of this review was to provide possible explanation about the possible interaction between pulmonary vascular beds and thyroid function in order to evaluate the possibility of novel perspectives in the general management of patients suffering from thyroid and cardiovascular diseases.