Glucose tolerance test

Uses

Alone

• For diagnosis of 'glucose intolerance' in pre-diabetic cases    .
• For diagnosis of insulinoma    .

In combination

• With insulin assays    , for diagnosis of insulinoma    .

Result data

Normal (reference) values

• In normal animal, plasma glucose rises immediately and then rapidly falls off to return to normal values usually within 2-3 hours.
• Glucose half-life 16-38 mins.
• K value 2.83 +/- 0.96.

Abnormal values

• Initially diabetic cats may have a reduced first phase of insulin secretion (2-15 min) followed by a delayed, exaggerated insulin response.
• Glucose intolerance , ie diabetes mellitus    , hyperadrenocorticism    second phase of insulin secretion is lost   →   glucose levels stay higher longer.
• Islet cell tumor , lower maximum plasma glucose levels and more rapid return to pre-glucose levels.

Errors and Artifacts

• Stress at sampling may result in longer half-life of glucose.

Sources

Publications

Refereed papers

• Feldhahn J R et al (1999) The effect of interday variation and a short term stressor on insulin sensitivity in clinically normal cats. J Fel Med Surg 1 (4), 233-240.
• Martin G J W et al (1999) Food intake and blood glucose in normal and diabetic cats fed ad libitum. J Fel Med Surg 1 (4), 241-251.
• Link K R J & Rand J S (1998) Reference values for glucose tolerance and glucose tolerance status in cats. JAVMA 213, 492-496.
• Link K R J, Rand J S & Hendrikz J K (1997) Evaluation of a simplified intravenous glucose tolerance test and a reflective glucose meter for use in cats. Vet Rec 140, 253-256.
• Sparkes A H, Adams D T, Cripps P J et al (1996) Inter and intraindividual variability in the reponse to intravenous glucose tolerance testing in cats. Am J Vet Res 57, 1294-1298.
• Nelson R W, Himsel C A, Feldman E C & Bottoms G D (1990) Glucose tolerance and insulin response in normal weight and obese cats. Am J Vet Res 51, 1357-1362.

Other sources of information

• Norton F (1985) The normal feline intravenous glucose tolerance test curve and concurrent insulin response curve. Proc 3rd Ann Med Forum, San Diego.