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Exaggeration of defective platelet function by methyldopa in hypothyroidism
American Journal of Hematology
|August 1, 1984
Summary
Methyldopa medication may worsen mild platelet dysfunction in hypothyroid patients, leading to prolonged bleeding times and abnormal platelet aggregation. Normalizing thyroid levels improved these platelet function defects.
Area of Science:
- Hematology
- Endocrinology
Background:
- Hypothyroidism is associated with mild platelet dysfunction.
- Methyldopa is a medication used to treat hypertension.
Observation:
- Two hypothyroid patients taking methyldopa exhibited significantly prolonged bleeding times (33 and 26 minutes) and abnormal platelet aggregation responses to various agonists.
- Seven hypothyroid patients not taking methyldopa had normal bleeding times and platelet aggregation.
Findings:
- In one patient, repeat studies while euthyroid and on methyldopa showed improved bleeding time (11 minutes), increased platelet retention (31% to 75%), and normalized aggregation responses.
- Factor VIII-related activities remained normal in all tested patients.
Implications:
- Methyldopa may potentiate the underlying platelet function defect in hypothyroidism.
- This interaction could contribute to an increased risk of bleeding in hypothyroid patients using methyldopa.