Impact Of Hypothyroidism On Coagulation Parameters, Implications For Early Hemostatic Screening

Abstract

Objective: Thyroid hormones interact closely with the coagulation and fibrinolytic systems, yet coagulation testing is not part of routine hypothyroidism work-up. This study compared coagulation parameters between people with hypothyroidism and people with normal thyroid function, and examined whether thyroid hormone levels correlate with these parameters, to build the case for coagulation screening in hypothyroidism.

Methods: In this comparative study, 200 adults were allocated to two groups of 100 each: euthyroid controls and patients with hypothyroidism, based on serum thyroid-stimulating hormone, triiodothyronine, and thyroxine levels. Prothrombin time, activated partial thromboplastin time, 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 assessed with Pearson correlation.

Results: The hypothyroid and control groups differed significantly in every coagulation marker studied (p<0.001). The hypothyroid group showed a longer activated partial thromboplastin time (43.0±7.3 seconds versus 32.0±3.1 seconds in controls), a shorter prothrombin time (10.7±0.6 seconds versus 12.1±0.5 seconds in controls), a lower plasma fibrinogen (233.0±47.7 mg/dL versus 270.0±47.2 mg/dL), and a higher plasma D-dimer than controls. Correlation between individual thyroid hormones and coagulation markers was generally weak, except for a strong positive correlation between thyroid-stimulating hormone and fibrinogen within the hypothyroid group (r=0.999, p<0.001).

Conclusion: Hypothyroidism is associated with a distinct coagulation profile relative to euthyroid individuals, most notably a longer activated partial thromboplastin time and lower fibrinogen, consistent with a hypo-coagulable tendency, alongside a shorter prothrombin time. These findings support incorporating basic coagulation screening into the clinical evaluation of hypothyroid patients, particularly before invasive or surgical procedures.