Homeostatic mechanisms normally maintain the plasma glucose concentration within narrow limits despite major fluctuations in supply and demand. There is increasing evidence that the growth hormone (GH)-insulin-like growth factor (IGF) axis may play an important role in glucose metabolism. GH has potent effects on intermediary metabolism, some of which antagonize the actions of insulin. In contrast, IGF-I has insulin-like actions, which are, in the case of glucose metabolism, opposite to those of GH. There is often deranged glucose metabolism in situations where GH is deficient or in excess. The clinical administration of GH or IGF-I results in altered glucose metabolism and changes in insulin resistance. Despite these observations, the precise role of GH and IGF-I and their interactions with insulin in controlling normal glucose homeostasis are unknown. In diabetes, GH secretion is abnormally increased as a result of reduced portal insulin resulting in impaired hepatic IGF-I generation. Evidence suggests that this may contribute to the development of diabetic microvascular complications. IGF-I 'replacement' in diabetes is under investigation and new methods of delivering IGF-I as a complex with IGFBP-3 offer exciting new prospects.

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Disturbance of vision commonly accompanies hypoglycaemia. This study was designed to investigate the nature of the visual disturbance, the blood glucose threshold at which the disturbance occurred and the physiological basis. Measurements were made of the corrected visual acuity, colour vision (100 Hue test), visual evoked potentials (VEP), electroencephalography (EEG) frequency analysis and psychometry (digit recall) during stepwise induction of controlled hypoglycaemia produced by an intravenous insulin infusion. Six male volunteers and five insulin-dependent diabetic subjects were studied. During hypoglycaemia corrected visual acuity was unchanged. Colour vision was significantly impaired. Baseline VEP were normal in both groups but significantly prolonged during hypoglycaemia (mean increment 10.8 ms) and increased by greater than 5 ms in nine out of 11 subjects. Quantitative EEG analysis demonstrated slowing with a power density spectral shift from fast alpha to slow alpha, theta and delta which correlated with VEP latency and amplitude changes. The findings have clinical implications. A deterioration in colour vision is likely to impair the ability to read reagent strips by eye. VEP measurements in diabetic patients are likely to be misleading if hypoglycaemia is present; EEG changes are a sensitive index of cortical dysfunction during hypoglycaemia and provide a theoretical basis for developing a portable device to detect early hypoglycaemia.

1. Non-invasive aortic compliance measurements have been used previously to assess the distensibility of the aorta in several pathological conditions associated with increased cardiovascular risk. In adult patients with familial hypercholesterolaemia and those with growth hormone deficiency, aortic compliance has been found to correlate inversely with plasma cholesterol levels and age. We set out to establish if a relationship existed between the biophysical measurement of aortic compliance and biochemical variables in normal healthy adult subjects. 2. Blood pressure-corrected aortic distensibility, fasting insulin, insulin-like growth factor-I, total cholesterol, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol and triacylglycerol were measured in 38 (18 males, 20 females) normotensive healthy adults. 3. Blood pressure-corrected aortic distensibility was found to correlate inversely with age (r = -0.67, P < 0.001), low-density lipoprotein-cholesterol (r = -0.37, P < 0.02) and the low-density lipoprotein-/high density lipoprotein-cholesterol ratio (r = -0.33, P < 0.05) and positively with insulin-like growth factor-I (r = 0.47, P < 0.01). On separate analysis by sex, significant inverse correlations were observed in females between aortic distensibility and total cholesterol (r = -0.50, P < 0.02), low-density lipoprotein-cholesterol (r = -0.55, P < 0.01) and age (r = -0.74, P < 0.001). A positive correlation was found between aortic distensibility and insulin-like growth factor-I (r = 0.48, P < 0.05). On forced stepwise regression analysis, however, only age (P < 0.02) was found to be significant. In males, an inverse correlation was found between aortic distensibility and age (r = -0.57, P < 0.01), low-density lipoprotein-cholesterol (r = -0.51, P < 0.05), and the low-density lipoprotein-/high-density lipoprotein-cholesterol ratio (r = -0.63, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)