RESUMEN
PURPOSE: Thyroid-stimulating hormone (TSH) has a pulsatile and circadian rhythm in healthy individuals. We aimed to evaluate the diurnal changes of free thyroid hormones and serum TSH levels in patients with end-stage renal failure (ESRF) whose thyroidal functions are at normal ranges. METHODS: Thirty hemodialysis patients with chronic renal failure and without a known thyroidal disease who are over 18 and 35 healthy individuals were included. The serum TSH, free T3, and free T4 levels were examined among the patient and control group which were taken at 8:00 a.m., 4:00 p.m., and 0:00 a.m. RESULTS: Twenty-two (73.3%) patients were male, and the mean age of the patient group was 64 (sd = 14.45 years). Seventeen (48.6%) of the control group were female, and the mean age was 31.9 (sd = 6.4 years). Serum free T3 levels, measured at three different time points (8:00 a.m., 4:00 p.m., and 0:00 a.m.), were significantly lower in the patient group than in the control group and serum free T4 levels were measured at three different time points (8:00 am, 4:00 p.m., and 0:00 a.m.) were significantly higher in the patient group than in the control group. Serum TSH levels were higher in the patient group than in the control group at 08:00, and were lower at 24:00 (p < 0.001). The nocturnal increase of serum TSH level under 0.525 suggested diurnal rhythm disruption with 83% sensitivity and 87% specificity. CONCLUSION: The nocturnal serum TSH increase is not seen in ESRF patients who did not have a thyroid disease. We think that not observing a nocturnal TSH increase could be an early indication of the sick euthyroid syndrome.
