Free thyroxine, free triiodothyronine and thyroid-stimulating hormone before and after hemodialysis in Saudi patients with end-stage renal disease: is there any difference?

Patients on regular hemodialysis (HD) suffer from a chronic illness that is believed not to involve the thyroid gland. However, they may have low levels of serum thyroxine (T4) and tri-iodothyronine (T3). It was found earlier that serum total T3 and free T4 concentrations were significantly higher immediately after a HD session than before. In this single-center prospective study, we evaluated the difference between free T3 (FT3), free T4 (FT4) and thyroid-stimulating hormone (TSH) levels before and immediately after HD sessions in 40 Saudi patients with end-stage renal disease undergoing regular HD at the Prince Salman Center for Kidney Disease, Riyadh, Saudi Arabia. The study involved 23 female and 17 male patients with a mean age of 49.65 ± 16.20 years. None of the study patients had any known thyroid disease. We measured the thyroid hormones monthly for three successive months using the electrochemiluminescence technique both before and after HD sessions. At the end of our study, we found a statistically significant difference between pre-HD and post-HD levels for FT3; in the first month, it was 4.47 ± 1.01 versus 4.86 ± 1.03 pmol/L, (P = 0.004); in the second month, it was 4.48 ± 1.37 versus 4.83 ± 1.64 pmol/L, (P = 0.008); and in the third month, it was 3.84 ± 0.88 versus 4.04 ± 0.84 pmol/L, (P = 0.003). The FT4 in the first month was 15.42 ± 2.75 pmol/L versus 17.20 ± 2.85 pmol/L, P = 0.000, in the second month it was 14.86 ± 2.66 versus 16.74 ± 3.27 pmol/L, P = 0.000 and in the third month it was 14.86 ± 3.93 versus 16.70 ± 4.00 pmol/L, P = 0.000, respectively. However, the pre- and post-HD levels of TSH did not show any statistically significant difference; in the first month it was 3.17 ± 1.47 versus 3.32 ± 1.39 pmol/L, P = 0.254, in the second month it was 2.57 ± 1.36 versus 2.49 ± 1.29 pmol/L, P = 0.299 and in the third month it was 2.36 ± 1.17 versus 2.44 ± 1.22 pmol/L, P = 0.238, respectively. Thus, there was a statistically significant increase in the post-HD levels of FT3 and FT4 although the TSH levels did not show any significant change. Our study suggests that measurement of TSH alone might be more reliable in the assessment of thyroid function in patients on regular HD than FT3 and FT4.