Early Hemostatic Screening in Hyperthyroidism: A Comparative Study of Coagulation Parameters in Hyperthyroid and Euthyroid Adults

Abstract

Objective: Thyroid hormones interact closely with coagulation and fibrinolytic systems. However, coagulation testing is not routinely included in thyroid evaluations. This study compared coagulation parameters between adults with hyperthyroidism and euthyroid controls and assessed correlations between thyroid hormone levels and these parameters to evaluate the rationale for early hemostatic screening in hyperthyroidism.

Methods: This comparative, cross-sectional study included 200 adults divided into two groups of 100: euthyroid controls and patients with hyperthyroidism, classified according to serum thyroid-stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4) levels. Prothrombin time (PT) activated partial thromboplastin time (aPTT), plasma fibrinogen, and plasma D-dimer were measured and compared between groups using the independent-samples t-test. Associations between thyroid hormones and coagulation markers were evaluated using Pearson correlation analysis.

Results: Significant differences were observed between the hyperthyroid and control groups for all coagulation markers studied (p<0.001). The hyperthyroid group exhibited a shorter aPTT (28.4±7.0 s vs. 32.0±3.1 s), a shorter PT (10.5±0.6 s vs. 12.1±0.5 s), higher plasma fibrinogen (375.0±79.4 mg/dL vs. 270.0±47.2 mg/dL), and substantially higher plasma D-dimer (500.5±241.2 ng/mL vs. 137.1±71.7 ng/mL) compared to controls. Correlations between individual thyroid hormones and coagulation markers were generally weak, except for a strong positive correlation between TSH and fibrinogen in the hyperthyroid group (r=0.999, p<0.001).

Conclusion: Hyperthyroidism is associated with a distinct coagulation profile compared to euthyroid individuals, characterized by shortened aPTT and PT, as well as elevated fibrinogen and D-dimer levels, indicating a hypercoagulable and relatively hypofibrinolytic state. These findings support the inclusion of basic coagulation screening in the routine clinical evaluation of hyperthyroid patients, especially prior to invasive or surgical procedures.