小児期甲状腺機能亢進症におけるインスリン・グルカゴン・成長ホルモン分泌能

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There are many reports of glucose intolerance in adult patients with hyperthyroidism but few reports of glucose intolerance in hyperthyroid children. In this study, we measured plasma levels of glucose, insulin, glucagon and growth hormone in hyperthyroid children and control subjects by the use of three kinds of tolerance tests : an oral glucose tolerance test, an arginine tolerance test and an insulin tolerance test. In the oral glucose tolerance test, mean fasting glucose levels (79.6 ± 1.4 mg/dl) rose to maximum levels (157.3 ± 4.3 mg/dl) at 30 min in hyperthyroid children which were significantly higher than the levels in control subjects (p<0.01). The maximum levels of glucose fell slowly and returned to fasting levels at 180 min. In this test, plasma insulin levels increased from basal levels (12.7 ±1.9 μU/ml) to maximum levels (120.8± 22.1.μU/ml) at 30 min in the prepubertal age group of hyperthyroidism. On the other hand, in the pubertal age group of hyperthyroidism, maximum levels of insulin were observed at 60 min, but not at 30 min. These maximum levels of insulin of both hyperthyroid age groups were significantly higher than those in the control subjects (p<0.05, p<0.01 respectively). There was no difference in insulin-glucose ratio at 30 min (ΔIRI/ΔBG) and insulinogenic index (I.I.) at 0 to 60 min between these two groups of hyperthyroid children and control subjects. However, I.I. at 0 to 120 min and 0 to 180 min decreased significantly in the pubertal age group of hyperthyroidism as compared with those in the control group (p<0.05, p<0.02 respectively). In the oral glucose tolerance test, plasma glucagon levels decreased from basal levels (74.1 ± 4.3 pg/ml) to minimum levels (36.4 ± 4.7 pg/ml) at 90 min in hyperthyroidism, which were significantly lower than those in the controls (p<0.05). However : there was no difference in -ΣΔAIRG/ΣΔBG (cummurative glucagon response/cummurative glucose response) between the subjects with hyperthyroidism and the controls. On the other hand, lower responses of blood glucose, insulin, glucagon and growth hormone to arginine were observed in subjects with hyperthyroidism than in the controls.<BR>Moreover in the insulin tolerance test, there was no difference in glucagon and growth hormone response between the subjects with hyperthyroidism and the controls.<BR>Thus our conclusions are as follows : 1) A marked increase in blood glucose after oral glucose load was observed in spite of normal insulin-glucose ratio in hyperthyroid children, suggesting the existence of peripheral insulin resistance. 2) In the pubertal age group, as indicated by the decrease of LI., insulin insufficiency may also be responsible for glucose intolerance in hyperthyroidism. 3) Adequate suppression of glucagon to oral glucose load was observed in the subjects with hyperthyroidsm and the controls, suggesting that there is no difference in pancreatic A-cell sensitivity to glucose between hyperthyroidism and controls. 4) Lower responses of insulin and glucagon to arginine in the subjects with hyperthyroidism compared with those in the controls were observed, suggesting that the islets of Langerhans are insensitive to arginine in hyperthyroidism. 5) Adequate growth hormone response to insulin-induced hypoglycemia was observed in the subjects with hyperthyroidism, suggesting that growth hormone is secreted normally.

小児期甲状腺機能亢進症におけるインスリン・グルカゴン・成長ホルモン分泌能

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