Changes in serum levels of thyroxine and thyroxine-binding proteins (TBG, TBPA, ALBUMIN) induced by venous stasis.

Serum concentrations of thyroxine (T4), thyroxine-binding globulin (TBG), thyroxine-binding pre-albumin (TBPA) and albumin were determined in 21 healthy, young subjects before and after a brief venous stasis in two experiments: 1) 3 min stasis induced by a sphygmomanometer with constant pressure 20 mmHg above the diastolic blood pressure and 2) 2 min stasis induced by an arm tourniquet of rubber. In both experiments the serum T4 level was significantly rised (mean 9%) after venous compression. Increases of the same magnitude were observed for serum TBG, serum TBPA and serum albumin. The serum concentrations of the free constituents--sodium and creatinine--remained unchanged, whereas the haemoglobin concentration increased (mean 8%). This haemoconcentrating effect of venous stasis seemed to be more pronounced in females than in males. Our data emphasize the need for protein correction procedures when total serum T4 is measured.