Effect of experimental hypothyroidism on glomerular filtration rate and plasma creatinine concentration in dogs.
BACKGROUND
Hypothyroidism affects renal function in a manner opposite the effects of hyperthyroidism.


OBJECTIVE
To evaluate the effects of experimentally induced hypothyroidism on glomerular filtration rate (GFR) and basal plasma creatinine concentration in dogs.


METHODS
Sixteen anestrous, female dogs.


METHODS
Hypothyroidism was induced by administration of (131)I in 8 dogs, and 8 healthy euthyroid dogs acted as controls. Exogenous plasma creatinine clearance (an estimate of GFR) was measured in all dogs before (control period) and 43-50 weeks after induction of hypothyroidism (posttreatment period). Other pharmacokinetic parameters of creatinine were also determined.


RESULTS
No significant difference was observed for basal plasma creatinine concentration and creatinine clearance between control and hypothyroid dogs in the control period. In the posttreatment period, mean + or - SD creatinine clearance in the hypothyroid group (2.13 + or - 0.48 mL/min/kg) was lower (P < .001) than that of the control group (3.20 + or - 0.42 mL/kg/min). Nevertheless, basal plasma creatinine concentrations were not significantly different between the hypothyroid and control groups (0.74 + or - 0.18 versus 0.70 + or - 0.08 mg/dL, respectively) because endogenous production of creatinine was decreased in hypothyroid dogs (22 + or - 3 versus 32 + or - 5 mg/kg/d, P=.001).


CONCLUSIONS
Hypothyroidism causes a substantial decrease in GFR without altering plasma creatinine concentrations, indicating that GFR evaluation is needed to identify renal dysfunction in such patients.
Panciera
D L
DL
Department of Small Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, USA. panciera@vt.edu
Lefebvre
H P
HP
D000818:Animals; D002712:Chlorides / Q000097:blood; D003404:Creatinine / Q000097:blood*; D004283:Dog Diseases / Q000097:blood / Q000503:physiopathology*; D004285:Dogs; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology / Q000662:veterinary*; D007037:Hypothyroidism / Q000097:blood / Q000503:physiopathology / Q000662:veterinary*; D007674:Kidney Diseases / Q000097:blood / Q000503:physiopathology / Q000662:veterinary*; D011897:Random Allocation; D013974:Thyroxine / Q000097:blood
D002712:Chlorides; D003404:Creatinine; D013974:Thyroxine