Consistent Reversible Elevations of Serum Creatinine Levels in Severe Hypothyroidism

Abstract

CERTAIN EFFECTS of the hypothyroid state on the kidney are well established. Histological changes have been demonstrated in both rats¹ and humans.^2,3 Physiological effects include changes in water and electrolyte metabolism, notably hyponatremia, and reliable alterations of renal hemodynamics,^4-11 including decrements in renal blood flow, renal plasma flow, glomerular filtration rate (GFR), and single nephron GFR. In 1 study⁴ GFR failed to reach the levels seen in euthyroid controls following the initiation of thyroid hormone replacement therapy, leaving open the possibility that the effect was not fully reversible. The cause of the decreased renal plasma flow and GFR observed is believed to be principally due to the generalized hypodynamic state of the circulatory system in hypothyroidism.¹²