The prognostic impact of thyroid function in pulmonary hypertension

Abstract

Background: Thyroid disease is common in patients with pulmonary hypertension (PH), but its effect on long-term survival remains unknown. We examined the prognostic significance of thyroid hormone levels of free triiodothyronine (fT3) and free thyroxine and thyroid-stimulating hormone (TSH), and thyroid hormone replacement (THR) therapy in PH.

Methods: We conducted a retrospective analysis of 1,756 patients enrolled in the Giessen PH Registry in 1999 to 2013 with baseline thyroid function data; of these, 355, 533, 498, and 370 had pulmonary arterial hypertension (PAH); including 192 with idiopathic PAH (iPAH), PH due to left heart disease, PH due to lung diseases, and chronic thromboembolic PH (CTEPH), respectively. Thyroid function parameters associated with mortality were identified using Cox regression and Kaplan-Meier analyses.

Results: Transplant-free survival at 1, 3, and 5 years was 86.7%, 65.6%, and 53.0%, respectively. Absence of THR therapy was an independent predictor of death in iPAH (multivariate hazard ratio [HR], 2.50; 95% confidence interval [CI], 1.06-5.75). In patients without THR therapy, TSH levels in the lowest and highest quartiles (compared with the middle 2 quartiles) independently predicted death in iPAH (HR, 1.98; 95% CI, 1.07-3.67), whereas reduced fT3 levels were independently associated with increased death in PAH (HR, 8.30; 95% CI, 2.50-25.00) and CTEPH (HR, 1.79; 95% CI, 1.14-4.20).

Conclusions: Thyroid hormone levels and THR therapy are prognostic factors in iPAH, PAH, and CTEPH. Prospective studies are warranted to verify the prognostic significance of thyroid function and the effect of THR therapy in PH.

Keywords: mortality; prognostic factor; pulmonary hypertension; survival; thyroid function.