title: Relationship between serum TSH levels and intrarenal hemodynamic parameters in euthyroid subjects.
abstract: OBJECTIVE
  Low thyroid function may be associated with a reduced glomerular filtration rate (GFR) calculated on the basis of creatinine metabolism. Thyroid hormone directly affects serum creatinine in muscle and low thyroid function might exert a similar direct effect in the kidney. The goal of the study was to evaluate this possibility by assessment of the inulin-based GFR and to examine the mechanism underlying the reduction of GFR.
  
  
  METHODS
  Renal and glomerular hemodynamics were assessed by simultaneous measurements of plasma clearance of para-aminohippurate (CPAH) and inulin (Cin) in 26 patients with serum creatinine <1.00 mg/dl and without thyroid disease. All subjects were normotensive with or without antihypertensive treatment and were kept in a sodium-replete state. Renal and glomerular hemodynamics were calculated using Gomez's formulae.
  
  
  RESULTS
  Serum TSH, including within the normal range (0.69-4.30 μIU/ml), was positively correlated with vascular resistance at the afferent arteriole (Ra) (r=0.609, P=0.0010), but not at the efferent arteriole (Re). Serum TSH was significantly and negatively correlated with renal plasma flow (RPF), renal blood flow (RBF), and GFR (r=-0.456, P=0.0192; r=-0.438, P=0.0252; r=-0.505, P=0.0086 respectively). In multiple regression analysis, serum TSH was significantly positively associated with Ra after adjustment for age and mean blood pressure.
  
  
  CONCLUSIONS
  These findings suggest that low thyroid function, even within the normal range, is associated with reduced RPF, RBF, and GFR, which might be caused by a preferential increase in Ra.
authors.affiliation: Departments of Nephrology, Osaka City University Graduate School of Medicine, 1-4-3, Asahi-machi, Abeno-ku, Osaka 545-8585, Japan. naranotsudadesu@infoseek.jp
authors.forename: Akihiro
authors.initials: A
authors.lastname: Tsuda
authors.forename: Masaaki
authors.initials: M
authors.lastname: Inaba
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Ichii
authors.forename: Akinobu
authors.initials: A
authors.lastname: Ochi
authors.forename: Yoshiteru
authors.initials: Y
authors.lastname: Ohno
authors.forename: Shinya
authors.initials: S
authors.lastname: Nakatani
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Yamada
authors.forename: Katsuhito
authors.initials: K
authors.lastname: Mori
authors.forename: Hideki
authors.initials: H
authors.lastname: Tahara
authors.forename: Eiji
authors.initials: E
authors.lastname: Ishimura
mesh_terms: D000328:Adult; D000368:Aged; D050197:Atherosclerosis / Q000209:etiology; D015415:Biomarkers / Q000097:blood; D001794:Blood Pressure; D003404:Creatinine / Q000097:blood / Q000378:metabolism*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000150:complications / Q000378:metabolism*; D007444:Inulin / Q000097:blood; D007564:Japan; D008297:Male; D008875:Middle Aged; D017597:Renal Blood Flow, Effective; D012079:Renal Circulation; D017595:Renal Plasma Flow; D012307:Risk Factors; D013972:Thyrotropin / Q000097:blood*; D014655:Vascular Resistance; D010130:p-Aminohippuric Acid / Q000097:blood*
chemical_list: D015415:Biomarkers; D013972:Thyrotropin; D007444:Inulin; D003404:Creatinine; D010130:p-Aminohippuric Acid