Thyroid Function with Continuous KRT: A Prospective Study

Area of Science:

• Nephrology
• Endocrinology
• Critical Care Medicine

Background:

• Acute kidney injury (AKI) and end-stage kidney disease (ESKD) requiring continuous kidney replacement therapy (CKRT) are associated with high mortality.
• CKRT can clear solutes up to 40 kDa, including thyroid hormones like thyroid stimulating hormone (TSH), free thyroxine (fT4), and free triiodothyronine (fT3).
• The impact of CKRT on thyroid function and the hypothalamic-pituitary-thyroid (HPT) axis remains unclear.

Purpose of the Study:

• To investigate the effect of CKRT on thyroid hormone levels, thyroid function, and the HPT axis.
• To determine the clearance of TSH, fT4, and fT3 by CKRT.
• To assess the prevalence and persistence of non-thyroidal illness syndrome (NTIS) in CKRT patients.

Main Methods:

• Prospective, single-center observational study of 50 ICU patients on CKRT and 50 controls.
• Measured serum TSH, fT4, fT3, and reverse T3 (rT3) at baseline and on days 1, 3, 8, and 14.
• Measured CKRT effluent for TSH, fT4, and fT3; adjudicated thyroid function status.

Main Results:

• CKRT patients exhibited lower fT4 and fT3 levels compared to controls, with more values below the normal range.
• TSH and fT4 were detected in CKRT effluent, confirming clearance.
• Severe and persistent NTIS was prevalent in the CKRT cohort; no patient achieved euthyroid status during CKRT.

Conclusions:

• This study is the first to evaluate thyroid function and hormone clearance during CKRT.
• The majority of CKRT patients develop severe, persistent NTIS, potentially influenced by CKRT-mediated hormone clearance.
• These findings suggest that NTIS during CKRT may contribute to the high mortality rates in AKI and ESKD patients.