Primary haemostasis in thyroid disease

. Objectives. There have been reports on a bleeding tendency in hypothyroidism resembling von Willebrand's disease. The aim of the present study was to investigate whether altered primary haemostasis is a general phenomenon in thyroid disease. Design/setting. A total of 10 patients with hyperthyroidism and nine patients with hypothyroidism were studied at diagnosis, and during treatment with carbimazole or L-thyroxine. respectively, when euthyroidism had been achieved. Results. In untreated hypothyroidism, template bleeding time was prolonged (median 9.3 min, range 3.8–20.0 min) compared to that in controls (median 4.0 min, range 3.0–6.0 min; P < 0.05). whereas maximal agglutination velocity induced by ristocetin was decreased (38% min−1, range 4–52% min−1 vs. 70% min−1, range 60–81% min−1, P < 0.05). The level of von Willebrand factor antigen in plasma from hypothyroid patients was less than half of the value in hyperthyroid patients. This difference disappeared after euthyroidism was achieved. Conclusions. We found that changed primary haemostasis is a general feature of hypothyroidism, and that it is resolved after levothyroxine treatment.