Stability of recombinant human thyrotropin potency based on bioassay in FRTL-5 cells.

Background: Recombinant human thyrotropin (rhTSH; Thyrogen®) is approved for use in a 0.9 mg dose/day for 2 consecutive days for diagnosis and treatment of differentiated thyroid cancer. It is recommended that it be injected immediately after reconstitution in the distilled water diluent supplied by the manufacturer. However, Thyrogen has been used off-label in doses less than the standard 0.9 mg dose for stimulation of radioiodine uptake in the treatment of multinodular goiter. To determine whether the biologic activity of Thyrogen can be preserved after dilution, we designed experiments to assess the biologic stability of Thyrogen under different durations and temperatures of storage. Methods: rhTSH was diluted in 1% bovine serum albumin in phosphate-buffered saline to a concentration of 0.9 mg/mL and further diluted to 0.1 mg/mL. Aliquots of 0.5 mL were stored at room temperature, 4°C, −11°C, and −60°C for various lengths of time. In addition, rhTSH aliquots were also subjected to incubation for 1 hour...