title: Repeated freezing and thawing does not generally alter assay results for several commonly studied reproductive hormones.
abstract: OBJECTIVE
  To determine the effect of repeated freezing and thawing, and storage temperature, on the assay results of commonly measured reproductive hormones, and sex hormone-binding globulin (SHBG) in human serum.
  
  
  METHODS
  Prospective laboratory study.
  
  
  METHODS
  Academic medical center.
  
  
  METHODS
  Four men and three pregnant women in the third trimester.
  
  
  METHODS
  Pooled serum from men and pregnant females were frozen at either -20 degrees C or -70 degrees C. Aliquots were then subjected to repeat freeze/thaw cycles, from 1 to 10 times, and assays were performed after the final freeze/thaw cycle.
  
  
  METHODS
  Assay results for eight hormones (FSH, LH, PRL, androstenedione (A), 17alpha-hydroxyprogesterone, P, insulin, and SHBG, as a function of the number of freeze/thaw cycles and storage temperature.
  
  
  RESULTS
  Only SHBG in male serum at -20 degrees C and P in pregnant serum at -70 degrees C showed statistically significant decreases in assay results with repeated freeze/thaw cycles (3.3% and 1.1% per cycle, respectively). All other analytes did not show significant changes as a function of freeze/thaw cycles or storage temperature.
  
  
  CONCLUSIONS
  There is no consistent or predictable alteration in the results of SHBG, or the glycoprotein and steroid hormones evaluated, as a function of repeated freeze/thaw or the storage temperature of human serum.
authors.affiliation: Department of Obstetrics and Gynecology, The University of Alabama at Birmingham, Birmingham, Alabama 35233-7333, USA.
authors.forename: R
authors.initials: R
authors.lastname: Reyna
authors.forename: K D
authors.initials: KD
authors.lastname: Traynor
authors.forename: G
authors.initials: G
authors.lastname: Hines
authors.forename: L R
authors.initials: LR
authors.lastname: Boots
authors.forename: R
authors.initials: R
authors.lastname: Azziz
mesh_terms: D001793:Blood Preservation; D015925:Cryopreservation; D005260:Female; D005615:Freezing; D006728:Hormones / Q000097:blood*; D006801:Humans; D008297:Male; D011247:Pregnancy; D011446:Prospective Studies; D012098:Reproduction / Q000502:physiology*; D012738:Sex Hormone-Binding Globulin / Q000032:analysis; D013696:Temperature
chemical_list: D006728:Hormones; D012738:Sex Hormone-Binding Globulin