Platelet Na+,K+-adenosine triphosphatase as a tissue marker of hyperthyroidism

Platelet Na+,K+-adenosine triphosphatase (ATPase) activity was measured in 34 (15 males, 19 females) healthy subjects, 89 (35 males, 54 females) hyper thyroid patients, and 34 (7 males, 27 females) treated hyperthyroid patient s to assess the potential of this measurement as a tissue marker and diagno stic test for hyperthyroidism. Platelet Na+,K+-ATPase activity was measured in platelet lysates by the rate of release of phosphate from adenosine tri phosphate (ATP) in the presence and absence of ouabain. Platelet Na+,K+-ATP ase activity (median and range) in the hyperthyroid group (271, 169 to 821 pmol/h/g protein) was significantly higher compared with the healthy group (125, 74 to 185 mu mol/h/g protein, P<.001 by Mann-Whitney U test). The tre ated hyperthyroid group had slightly, but significantly higher, free triiod othyronine (FT3) and free thyroxine (FT4), as well as platelet Na+,K+-ATPas e activity (147, 98 to 246 <mu>mol/h/g protein, P<.05). If a platelet Na+,K +-ATPase activity of 190 <mu>mol/h/g protein was used as a cut off value, t he specificity and sensitivity were 90% and 93%, respectively. We conclude that platelet Na+,K+-ATPase may be a useful tissue marker of hyperthyroidis m. Copyright (C) 2001 by W.B. Saunders Company.