title: Alterations in osmotic fragility of the red blood cells in hypo- and hyperthyroid patients.
abstract: BACKGROUND
  Changes in concentration of thyroid hormones can affect Na+-K+-ATPase number and activity and phospholipid composition of the cell membranes leading to changes in the surface to volume ratio and strength of membrane.
  
  
  OBJECTIVE
  In this study, the osmotic fragility of the red blood cells from non-treated hypo- and hyperthyroid patients was compared to that of control subjects.
  
  
  METHODS
  After 3 washings with normal saline, red blood cells were placed in varying concentrations of sodium chloride (Na- Cl) (0-0.9%) and fragility was assessed with colorimetric method; to do this, after the incubation period, tubes were centrifuged and the optical density of the tubes was measured. Hemolysis percentage in tubes was calculated based on 100% hemolysis in the tubes containing no NaCl (0%).
  
  
  RESULTS
  Osmotic fragility of the cells from hyperthyroid patients in 0.45% NaCl was significantly lower than control subjects (74.6%+/-30.2 vs 93.8%+/-9.1, p<0.01). The osmotic fragility of red blood cells in 0.5% concentration of sodium chloride in hyperthyroid patients was significantly lower compared to that of controls (27.8%+/-26.0 vs 63.5%+/-27.5, p<0.001). No significant difference was observed between the osmotic fragility of the hypothyroid patients compared with control subjects.
  
  
  CONCLUSIONS
  Alteration in osmotic fragility is seen in patients with hyperthyroidism; however, anemia reported in hypo- or hyperthyroid patients is not due to high osmotic fragility of red blood cells and other causes need to be investigated.
authors.affiliation: Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University, Tehran, Iran. zahedi@endocrine.ac.ir
authors.forename: S Zahedi
authors.initials: SZ
authors.lastname: Asl
authors.forename: N Khalili
authors.initials: NK
authors.lastname: Brojeni
authors.forename: A
authors.initials: A
authors.lastname: Ghasemi
authors.forename: F
authors.initials: F
authors.lastname: Faraji
authors.forename: M
authors.initials: M
authors.lastname: Hedayati
authors.forename: F
authors.initials: F
authors.lastname: Azizi