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[*] [**] [***]

Abstract

The effect of T therapy (T 0.5 and T 10) on BS, serum IRI and FFA levels of thyroidectomized dogs during an OGTT was studied.

Either T dose failed to restore the BS profiles in these animals: T 10 corrected the delayed onset of hyperglycemia after glucose load but it definitely raised the BS baseline; T 0.5 also enhanced this baseline and, also, reduced the magnitude of hyperglycemia.

Both T doses reduced the overnormal serum IRI levels observed in the thyroidectomized dogs both in the post-absorptive condition and during the test; T 10 was more effective than T 0.5; normal serum IRI levels, however, were not achieved during the test.

T therapy only partially corrected the serum FFA profiles of the thyroidectomized dogs. Both T 0.5 and T 10 restored both serum FFA baseline and return to baseline at the end of the test, but they overshot to overnormal serum FFA values during the fall early after glucose load.

Key words

Hypothyroidism - OGTT - Serum IRI - Serum FFA - Blood Sugar - Thyroxine - Dogs

1 This work was partially supported by Research Grant No. 2304-d from the Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.

2 These studies have been reported in abstract form (XXV International Congress of Physiological Sciences, Munich, Germany, July 25-31, 1971, Comm.No. 1400)

3 The following abbreviations will be used throughout this paper: T, thyroxine; T0.5, T10 and T100, thyroxine at the following doses: 0.5, 10 and 100 γ/kg body wt./d, for 11, 11 and 10 days, respectively; OGTT and IVGTT, oral and intravenous glucose tolerance test; BS, blood sugar; IRI, immunereactive insulin; FFA, free fatty acids; BEI, butanol extractable iodine.

1 This work was partially supported by Research Grant No. 2304-d from the Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.

2 These studies have been reported in abstract form (XXV International Congress of Physiological Sciences, Munich, Germany, July 25-31, 1971, Comm.No. 1400)

3 The following abbreviations will be used throughout this paper: T, thyroxine; T0.5, T10 and T100, thyroxine at the following doses: 0.5, 10 and 100 γ/kg body wt./d, for 11, 11 and 10 days, respectively; OGTT and IVGTT, oral and intravenous glucose tolerance test; BS, blood sugar; IRI, immunereactive insulin; FFA, free fatty acids; BEI, butanol extractable iodine.

4 Established investigator, Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.

5 Post-Graduated Research Fellow, University of Buenos Aires, Buenos Aires, Argentina.