Effect on renal function of restoration of euthyroidism in hyperthyroid cats with iatrogenic hypothyroidism

J Vet Intern Med. Jul-Aug 2014;28(4):1251-5. doi: 10.1111/jvim.12359. Epub 2014 Apr 28.

Abstract

Background: Iatrogenic hypothyroidism is associated with an increased incidence of azotemia after treatment of hyperthyroidism, and decreased survival time in azotemic hyperthyroid cats.

Hypothesis: Restoration of euthyroidism will decrease plasma creatinine concentrations.

Animals: Nineteen client-owned, methimazole- or carbimazole-treated, hyperthyroid cats with documented iatrogenic hypothyroidism (based on subnormal plasma total thyroxine concentrations [TT4] and increased plasma thyroid-stimulating hormone concentrations).

Methods: Prospective interventional study. Doses of antithyroid medication were reduced until euthyroidism was restored (TT4 10-40 nmol/L). Plasma creatinine concentration and selected other clinicopathologic variables were evaluated before and after restoration of euthyroidism and compared by nonparametric statistics. Data are presented as median [25th, 75th percentile].

Results: Restoration of euthyroidism was associated with a significant decrease in plasma creatinine concentrations (2.61 [1.90, 3.26] mg/dL versus 2.07 [1.42, 2.82] mg/dL; P < .001) and body weight (4.03 [3.59, 4.53] kg versus 3.89 [3.34, 4.18] kg; P = .019), and a significant increase in packed cell volume (30 [28, 39]% versus 34 [29, 39]%; P = .038), heart rate (174 [163, 201] bpm versus 190 [164, 202] bpm; P = .009), and plasma alkaline phosphatase activity (26.6 [17.0, 33.0] IU/L versus 38.0 [23.5, 46.5] IU/L; P < .001).

Conclusions and clinical importance: Restoration of euthyroidism in medically treated hyperthyroid cats with iatrogenic hypothyroidism causes a reduction in plasma creatinine concentrations, and thus might improve renal function; however, this could be influenced by concurrent changes in body weight.

Keywords: ALP; Anemia; Azotemia; CKD; PCV.

MeSH terms

  • Animals
  • Antithyroid Agents / adverse effects
  • Antithyroid Agents / therapeutic use
  • Azotemia / etiology
  • Azotemia / veterinary
  • Carbimazole / adverse effects
  • Carbimazole / therapeutic use
  • Cats
  • Creatinine / blood
  • Hyperthyroidism / complications
  • Hyperthyroidism / drug therapy
  • Hyperthyroidism / veterinary*
  • Hypothyroidism / chemically induced
  • Hypothyroidism / complications
  • Hypothyroidism / veterinary*
  • Iatrogenic Disease / veterinary
  • Kidney Diseases / etiology
  • Kidney Diseases / veterinary*
  • Methimazole / adverse effects
  • Methimazole / therapeutic use
  • Prospective Studies

Substances

  • Antithyroid Agents
  • Methimazole
  • Carbimazole
  • Creatinine