Hemostatic defects in response to aspirin challenge in hypothyroidism.

A patient with hypothyroidism had ingested aspirin and bled profusely following dental extraction. The only abnormalities noted on coagulation survey were a prolonged aspirin bleeding time and reduced retention of platelets on glass beads. Based on this index case, an additional 12 hypothyroid patients, on no medications, were evaluated for a mild bleeding disorder, including studies with aspirin challenge. The results indicate that thrombin-induced platelet serotonin release, following aspirin ingestion, was subnormal in most hypothyroid patients. However, only hypothyroid individuals with TSH levels of greater than 60 microU/ml have an increased hemostatic sensitivity to aspirin, as measured by the bleeding time test. These findings did not appear to result from decreased synthesis of the factor VIII-von Willebrand factor complex. As this drug is commonly ingested, the effects of aspirin on bleeding may explain the easy bruising and menorrhagia that occur in hypothyroid individuals.