Coagulation inhibitor in hypothyroidism.

A patient was referred for investigation of heavy bleeding after surgery. He showed several features of hypothyroidism but no goitre. Primary autoimmune hypothyroidism was confirmed by the finding of a low serum thyroxine concentration and a high thyrotropin concentration. Factor VIII concentration was low, and a mild coagulation inhibitor was found. The patient was treated with thyroxine and returned to normal health within a few months. The inhibitor found in this patient may have been specific for factor VIII, but the presence of coagulation inhibitors should be considered in patients with hypothyroidism.