ABNORMALITIES OF THYROTROPHIN (TSH) EVENING RISE AND PULSATILE RELEASE IN HAEMODIALYSIS PATIENTS: EVIDENCE FOR HYPOTHALAMIC‐PITUITARY CHANGES IN CHRONIC RENAL FAILURE

SUMMARY Using a sensitive enzyme amplified immunoassay for TSH, the evening rise and pulsatile release of TSH were studied in 10 men with chronic renal failure treated by haemodialysis. Compared to euthyroid male controls the evening rise of TSH was attenuated (median 0.066 vs 0.195 mU/l/h, P <0.01) and the rate of rise correlated with the TSH response to TRH (r= 0.93, P <0.001). All subjects showed TSH pulsatility in at least one method of data analysis but the less sensitive incremental method showed no significant difference in pulse frequency and amplitude between the two groups. However, with time series analysis, periodicity was shorter (median 45 vs 95 min, P= 0.013) and pulse amplitude smaller (median 0.06 vs 0.175 mU/l, P=0.017) in renal patients. Pulse amplitude, but not periodicity, correlated with the TSH response to TRH (r= 0.68, P <0.05). In addition, serum total thyroxine, free thyroxine and free triiodothyronine concentrations were reduced, while serum prolactin and 17 β-oestradiol concentrations were raised. These changes in TSH evening surge and pulsatile release may contribute to the reduction in thyroidal hormone concentrations seen in renal failure and emphasize the value of sensitive methods of hormone and pulse data analysis.