Serum Creatinine Level and Its Influencing Factors in Patients with Primary Hypothyroidism

  Objective  To explore the changes of serum creatinine (Cr) level in patients with primary hypothyroidism and the influencing factors of serum Cr level.

  Methods  We retrospectively analyzed the clinical data of 27 patients with primary hypothyroidism who were treated at Peking Union Medical College Hospital between January 2006 and December 2010. The patients were divided into two groups according to the level of serum free thyroxine (FT₄), i.e. clinical hypothyroidism group and subclinical hypothyroidism group. We calculated the creatinine clearance rate (CCr) with Cockcroft-Gault Formula and analyzed the relationship of serum Cr, blood urea nitrogen, and CCr with thyroid function and serum creatine kinase (CK).

  Results  The serum Cr levels in 14.8% of the patients exceeded the normal range. The serum levels of Cr were negtively correlated with free triiodothyronine (FT₃) (P < 0.0001, r=-0.628) and FT₄ (P=0.016, r=-0.458). The serum Cr level in the clinical hypothyroidism group was higher than in the subclinical hypothyroidism group(99.89±28.93)μmol/L vs. (74.67±8.03)μmol/L, P < 0.01. After thyroxine treatment, the serum level of FT₄ significantly increased (P=0.005) while the serum level of Cr significantly decreased (P=0.001). The serum Cr level was positively correlated with lnCK(P=0.032, r=0.596), and CCr was positively correlated with FT₄(P=0.043, r=0.527).

  Conclusions  Routine screening of thyroid function is recommended in patients with elevated serum Cr level. An increased serum Cr level is correlated with both the decrease of CCr and the damage of muscles. The level of serum Cr elevated due to hypothyroidism could return to normal range when the thyroid function recovers.