Horm Metab Res 1986; 18(11): 771-774
DOI: 10.1055/s-2007-1012432
Clinical

© Georg Thieme Verlag, Stuttgart · New York

An Elevation of BUN/Creatinine Ratio in Patients with Hyperthyroidism

T. Aizawa, K. Hiramatsu, H. Ohtsuka, M. Kobayashi, Y. Koizumi, T. Miyamoto, A. Niwa, T. Yamada
  • Department of Gerontology, Endocrinology and Metabolism School of Medicine, Shinshu University, Matsumoto, Japan
Further Information

Publication History

1985

1985

Publication Date:
14 March 2008 (online)

Summary

Blood urea nitrogen (BUN)/creatinine ratio was abnormally high (24.8 ± 0.6) in untreated hyperthyroid patients due to both increase in BUN and decrease in creatinine concentration. BUN, creatinine and BUN/creatinine ratio were all completely normalized after restoration of euthyroid status. On the other hand, BUN/creatinine ratio was slightly suppressed in hypothyroidisrn before treatment and it was reversed by thyroxine treatment (12.6 ± 4.0 and 16.3 ± 3.3, before and after treatment, respectively). An age-related increase in BUN/creatinine ratio, which was primarily due to an age-related increase in BUN, was also found in hyperthyroid subjects (21.9 ± 2.8 vs 27.7 ± 9.0; first vs fifth decade) and in normal controls (13.7 ± 2.8 vs 16.0 ± 2.9; first vs fifth decade).

To elucidate reasons for abnormal increase in BUN/creatinine ratio in hyperthyroidism, measurement of cardiac output and kinetic analysis on urea nitrogen (UN) and creatinine were performed. The results indicated a marked increase in cardiac output. Serum creatine concentration was clearly increased in hyperthyroid patients. Thus, serum creatinine concentration was suppressed due to a decrease in creatinine synthesis and an increase in renal creatinine excretion. BUN was high, primarily due to an increase in UN production secondary to excessive protein catabolism together with insufficient excretion of UN.