THYROID-CELL PROLIFERATION-INHIBITING ACTIVITY IN SERUM OF PATIENTS WITH CHRONIC-RENAL-FAILURE ON HEMODIALYSIS

To investigate the possible humoral factor(s) influencing thyroid cell activity in chronic renal failure, we measured serum activity which s timulates or inhibits the [H-3]thymidine incorporation by using a cult ured functioning rat thyroid cell line (FRTL-5 cells) in 17 patients o n hemodialysis and 19 healthy controls. Polyethylene glycol-treated se rum was centrifuged and FRTL-5 cells were cultured with the supernatan t. Thyroid stimulating activity was determined by [H-3]thymidine incor poration after incubation for 72 h. There was no significant differenc e in [H-3]thymidine incorporation between cultures incubated with pati ent and normal serum, suggesting the absence of the stimulating activi ty. But when patient serum was added to cultures together with 20 or 5 0 mu U/ml of TSH, the TSH-stimulated increase in [H-3]thymidine incorp oration was significantly decreased, indicating the presence of thyroi d inhibiting activity, which possibly inhibits the thyroid cell growth . This activity was not significantly altered by hemodialysis. No sign ificant correlation was observed between this activity and serum level s of thyroid hormones or the iodine concentration. Patients on hemodia lysis therefore have serum thyroid inhibiting activity which is nondia lysable, differs from iodine, and could influence the thyroid cell gro wth.