Repeated freezing and thawing does not generally alter assay results for several commonly studied reproductive hormones

Objective: To determine the effect of repeated freezing and thawing, and st orage temperature, on the assay results of commonly measured reproductive h ormones, and sex hormone-binding globulin (SHBG) in human serum. Design: Prospective laboratory study. Setting: Academic medical center. Patient(s): Four men and three pregnant women in the third trimester. Intervention(s): Pooled serum from men and pregnant females were frozen at either -20 degreesC or -70 degreesC. Aliquots were then subjected to repeat freeze/thaw cycles, from 1 to 10 times, and assays were performed after th e final freeze/thaw cycle. Main Outcome Measure(s): Assay results for eight hormones (FSH, LH, PRL, an drostenedione (A), 17 alpha -hydroxyprogesterone, P, insulin, and SHBG, as a function of the number of freeze/thaw cycles and storage temperature. Result(s): Only SHBG in male serum at -20 degreesC and P in pregnant serum at -70 degreesC 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. Conclusion(s): There is no consistent or predictable alteration in the resu lts of SHBG, or the glycoprotein and steroid hormones evaluated, as a funct ion of repeated freeze/thaw or the storage temperature of human serum. (Fer til Steril(R) 2001;76:823-5. (C) 2001 by American Society for Reproductive Medicine.).