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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