Evaluation of the respective influence of thyroid hormones and TSH on blood coagulation parameters after total thyroidectomy.
BACKGROUND
Several hemostatic abnormalities have been described in hypothyroidism, such as modification of coagulation proteins and bleeding tendency. Although thyroid hormone deficiency is considered to be responsible for these changes, the underlying mechanisms have not yet been established.


OBJECTIVE
To evaluate the respective influence of peripheral thyroid hormones (free thyroxine) and TSH on blood clotting by assessing coagulation parameters in patients with a history of total thyroidectomy for thyroid cancer, under three different conditions: induced hypothyroidism, euthyroid state, and following recombinant human TSH (rhTSH) administration.


METHODS
Coagulation parameters (platelet count, fibrinogen, international normalized ratio, prothrombin time, thrombin time, activated partial thromboplastin time (APTT), factor VIII activity ((FVIII:C), as well as von Willebrand factor antigen (VWF:Ag) and VWF activity using collagen binding assay (VWF:CBA)) were measured in patients with severe hypothyroidism following withdrawal of thyroid hormone replacement therapy, and in the same patients with euthyroidism after restoring replacement treatment (group A), and before and after administering rhTSH (group B).


RESULTS
FVIII:C, VWF:Ag, and VWF:CBA were significantly decreased (P<0.001), whereas APTT was significantly increased (P<0.001) in patients with severe hypothyroidism compared with patients in the euthyroid state. No changes in clotting parameters were observed in patients who received rhTSH therapy.


CONCLUSIONS
This prospective study shows that severe short-term hypothyroidism is associated with significantly lower levels of VWF:Ag, VWF:CBA, and FVIII:C. Administration of exogenous TSH has no effect on coagulation parameters. These findings suggest that thyroid hormone deficiency is likely to be the main cause of coagulation alterations in patients with hypothyroidism.
Departments of Endocrinology Hematology, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Avenue Hippocrate, 10, B-1200 Brussels, Belgium.
John
J
Yango
Orsalia
O
Alexopoulou
Stephane
S
Eeckhoudt
Cedric
C
Hermans
Chantal
C
Daumerie
D000328:Adult; D001777:Blood Coagulation / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005340:Fibrinogen / Q000378:metabolism; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013963:Thyroid Hormones / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood / Q000601:surgery; D013965:Thyroidectomy; D013972:Thyrotropin / Q000494:pharmacology*; D013974:Thyroxine / Q000097:blood
D013963:Thyroid Hormones; D005340:Fibrinogen; D013972:Thyrotropin; D013974:Thyroxine