Studies on the Effect of Hyperthyroidism on the Insulin Response to Hyperglycemia in the Dog

Abstract

247MilmJIn, A.E., J.A. RusseU: Some effects of purified growth hormone on carbohydrate metabolism in the rat. Endocrinology 47: 114 (1950) Park, C.R., D.H. Brown, M. Comblath, W.H. Daughaday, M.E. Krahl: The effect of growth hormone on glucose up-take by the isolated rat diaphragrn. J. biol Chern. 197: 151 (1952) Sehaleh, D.S., D.M. Kipnis: Abnormalities in carbohydrate tolerance associated with elevated nonesterified fatty acids. SummaryW,e studied the effect of hyperthyroidism on the insulin response to hyperglycemia in the dog during a standard oral (OGm and intravenous (lVGTn glucose tolerance test. The development of the hyperthyroid condition was elicited through chronic subcutaneous I-thyroxin treatment at one of the following doses: 0.5 and 100"1 Ikg body weightl day, for 10-12 days. Blood sugar and serum immunoreactive insulin (IR!) were measuredNormal fasting blood sugar and serum IRI levels remained unchanged in the dog, despite the thyroxin treatment. The rate of disappearance of intravenously injected glucose from blood was normal as weil However, a shorter tban normal, 50% diminished and late insulin response to glucose was found in the hyperthyroid group (both thyroxin levels).The blood sugar eurve during the OGTT was found to be normal during the mild degree of hyperthyroidism, which was accompanied with an earlier tban normal and moderately rnaintained insulin response to hyperglycemia, whose maximum was 25% above normal The blood sugar curve during the OGrr was normal in the severely hyperthyroid dogs only for the 60 minute-period following glucose administration. However, the blood sugar was still above controllevels 30 minutes later in this group. A definitely reduced (low,late and shorter than normal) insulin response to hyperglycemia was found after thyroxin treatment (high level), Horm. Metab. Res. 3: 247-251 (1971) K e y -W 0 r d s: Hyperthyroid Dog -Serum Immunoreaclive Insulin -Oral Glucose Tolerance Test -Intravenous Glucose Tolerance Test

Effects of Hypothyroidism on Serum Immunoreactive Insulin, Free Fatty Acids and Blood Sugar in the Dog as Tested for Oral Glucose Tolerance - Corrective Effects of Thyroxine Therapy

“…The opposite effects have been observed after T overdosage, as reviewed by Ingbar and Woeber (1969). Our results are in line with these findings, since both T 0.5 and T 10 therapies induce an enhancement in BS levels of the thyroidectomized dogs in the post-absorptive condition (as demonstrated in the present paper) while T 100 therapy has a little, non-significant effect on this parameter (Renauld et al 1973a). The effect of T 0.5 was apparently more evident than the one of TlO, but it is advisable to remember that T 10restores the abnormality of glucose space induced by thyroidectomy in the dog while T 0.5 is uneffective (Renauld et al 1972).…”

“…The effect of hypothyroidism on the insulin response to hyperglycemia was better observed during the oral (as shown here) than during the intravenous glucose tolerance test (Renauld et al 1972(Renauld et al , 1973a. In contrast, the corrective effect of T therapy on this parameter was better observed du ring the latter.…”

“…Thus, while partial improvement of the abnormalities of BS promes in thyroidectomized dogs was found after both T 10 (as shown here) and T 100 therapies (Renauld et al 1973a), very flat BS curves were observed after T 0.5 therapy.…”

“…Nevertheless, this moderate reduction can not be the sole explanation for the very high serum IRI levels achieved in thyroidectomized dogs during the IVGTT (Renauld et al 1972(Renauld et al , 1973a and OGrr (as shown here). Therefore, we conclude that insulin secretion was overnormal during either test.…”

“…Sverdlik. Andrade and Rodriguez 1972); overshooting to hyperthyroidism and full inhibition of the insulin response to glucose du ring both tests followed T 100 therapy (Renauld et al 1973a). T 100 also reduced to 50% this response in normal dogs (Renauld, Pinto, Sverdlik and Foglia 1971a) whenever pituitary gland was present (Renauld.…”