Title page for ETD etd-04292008-104833


Type of Document Master's Thesis
Author Inteeworn, Natalie
URN etd-04292008-104833
Title The Effect of Hypothyroidism on Glucose Tolerance in Dogs
Degree Master of Science
Department Veterinary Medical Sciences
Advisory Committee
Advisor Name Title
Panciera, David L. Committee Chair
Monroe, William Edward Committee Member
Saker, Korinn E. Committee Member
Keywords
  • FSIGT and minimal model analysis
  • hypothyroidism
  • glucose tolerance
  • dog
  • insulin sensitivity
Date of Defense 2008-04-17
Availability unrestricted
Abstract
Background: Canine hypothyroidism is thought to cause abnormalities in glucose homeostasis, but the effect on glucose tolerance and insulin sensitivity has not been determined to date.

Hypothesis/Objectives: The purpose of the study was to investigate whether hypothyroidism has an effect on glucose tolerance and insulin sensitivity in dogs. We hypothesized that hypothyroidism causes insulin resistance.

Animals: Sixteen euthyroid bitches were randomly selected and allocated into two groups. In 8 dogs, hypothyroidism was induced by administration of 1 mCi/kg I-131. Experiments were performed on non-anesthetized, fasted dogs in anestrous approximately 12 months after hypothyroidism was induced.

Methods: The insulin-modified frequently sampled intravenous glucose tolerance test (FSIGT) and minimal model analysis were used to determine basal insulin and glucose concentrations, acute insulin response to glucose (AIRg), insulin sensitivity (SI), glucose effectiveness (SG) and the disposition index (DI).

Results: In the hypothyroid group, basal glucose concentrations were mildly decreased (P = 0.0079), whereas basal insulin was increased (P = 0.019). Insulin sensitivity was reduced in the hypothyroid group (P<0.001), whereas AIRg was higher (P=0.01). Other parameters were not different between groups.

Conclusions/Clinical Importance: Hypothyroidism negatively affects glucose homeostasis by inducing insulin resistance. In hypothyroid dogs, the disposition index (insulin sensitivity x insulin secretion) remained unchanged due to a compensatory increase in insulin secretion, thereby maintaining glucose tolerance. In cases with impaired insulin secretion, such as canine diabetes mellitus, concurrent hypothyroidism can have important clinical implications in the successful management of the disease.

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