Acute effect of low-calorie and low-carbohydrate diet on serum triiodothyronine-response to glucose ingestion and its relation to glucose tolerance.

This study was conducted to elucidate the mechanism of glucose intolerance due to carbohydrate restriction. 15 non-diabetic patients, aged 51 +/- 3 yr, were placed under dietary condition-I (2,012 kcal/day; carbohydrate 299 g) for more than 3 days after admission and then condition-I was substituted by condition-II (1,156 kcal/day; carbohydrate 139 g) for 2 weeks. At the end of condition-I and -II, 75 g OGTT was performed. After the comparison between condition-I and -II, patients were subdivided into two groups, namely, glucose tolerance-improved (n = 8) and -impaired (n = 7) groups. In the former, sigma glucose (mg/dl) during OGTT decreased from 898.1 +/- 28.0 to 738.5 +/- 36.0 (p < 0.05) and sigma IRI (microU/ml) decreased from 418.8 +/- 60.1 to 300.7 +/- 33.5 (p < 0.05) but sigma dT3 (ng/dl) increased from 11.3 +/- 14.7 to 70.3 +/- 15.1 (p < 0.05). In the latter, sigma glucose (mg/dl) increased from 774.6 +/- 46.6 to 867.1 +/- 50.1 (p < 0.05) and sigma IRI (microU/ml) increased from 323.4 +/- 47.8 to 400.8 +/- 47.8 (p < 0.05) but sigma dT3 (ng/dl) decreased from 45.3 +/- 7.1 to 20.0 +/- 14.7 although it did not reach a level of statistical significance. These results suggest that blunted serum T3-response to glucose ingestion is linked to the mechanism of glucose intolerance due to carbohydrate restriction.