Studies on the effect of the pre-exercise ingestion of carbohydrate on metabolism and performance have produced conflicting results, perhaps because of differences in the designs of the studies. The purpose of the present study was to examine the effects of ingesting differing amounts of glucose pre-exercise on the glucose and insulin responses during exercise and on time-trial (TT) performance. Nine well-trained male cyclists completed four exercise trials separated by at least 3 days. At 45 min before the start of exercise subjects consumed 500 ml of a beverage containing either 0 g (PLAC), 25 g (LOW), 75 g (MED) or 200 g (HIGH) of glucose. The exercise trials consisted of 20 min of submaximal steady-state exercise (SS) at 65% of maximal power output immediately followed by a [mean (SEM)] 691 (12) kJ TT. Plasma insulin concentrations at the onset of exercise were significantly higher ( P<0.05) in MED and HIGH compared with LOW and PLAC. Plasma glucose concentration fell rapidly ( P<0.05) during SS exercise in all glucose trials, but remained steady in PLAC. No difference in plasma glucose concentration was observed between the glucose trials at any time. Hypoglycaemia (less than 3.5 mmol.l(-1)) was observed in six subjects during SS but only after ingesting glucose pre-exercise. However, there was no difference in TT performance between the four trials. The ingestion of 0, 25, 75 or 200 g of glucose 45 min before a 20 min submaximal exercise bout did not affect subsequent TT performance. In addition, mild rebound hypoglycaemia following pre-exercise glucose ingestion did not negatively affect performance.

Salt Lake City, UtahFifty-three patients with renal failure on chronic hemodialysis were screened for the presence of goiter. Thirty-one had enlarged thyroid glands, a prevalence of goiter of 58% not previously reported. Thyroid function studies showed low 131 l uptakes, low serum thyroxine and normal serum triiodothyronine and thyrotrophic hormone levels. Serum concentrations of thyroxine-binding globulin were normal; serum albumin concentration was only slightly reduced. Administration of synthetic thyrotrophin-releasing hormone was followed by a rise in serum thyrotrophin and triiodothyronine levels. The cause of the goiter is not known. The possibility that goitrogenic substances are involved is discussed.ALTHOUGH A NUMBER of disturbances in thyroid function have been described in patients with renal failure on chronic hemodialysis (1-3), thyroid enlargement has not been recorded. We have noted the frequent occurrence of goiter in such patients, and for this reason we conducted a systematic study of thyroid function in patients with chronic renal failure on chronic hemodialysis. The results are reported here. Patients and MethodsForty-two patients with renal failure (17 men and 25 women, ages 14 to 35 years) undergoing chronic hemodialysis in the Home Dialysis Training Center at the University of Utah Medical Center and 11 patients with renal failure (10 men and 1 woman, ages 43 to 63 years) on chronic dialysis at the Veterans Administration Hospital in Salt Lake City were screened for goiter. The mean age for the total population studied was 40 years (range, 14 to 61 years). For comparison, we examined 100 persons without renal disease who lived in the same geographic area. The age range (14 to 61 years), the mean age (39 years), and the sex ratio (53 males and 47 females) were similar to those of the patients with chronic renal failure. Goiter was defined as an "enlargement of the thyroid gland to at least twice its normal size, as estimated by palpation of the neck by three different observers." The classification recommended by the World Health Organization (4) was also used.All the patients at the Home Dialysis Training Center at the University of Utah received the following medications: a phosphate binder (aluminum hydroxide), calcium carbonate, multivitamins, and 100-mg, biweekly intramuscular injections of testosterone cypionate (Upjohn Co., Kalamazoo, Michigan). The patients at the Veterans Administration Hospital took the same oral medications but did not receive testosterone. No patients were restricted as to protein intake, and all were dialyzed three times per week, 5 to 6 hours per dialysis, using heparin as the anticoagulant. The patients had been on dialysis from 1 to 48 months (mean, 10 months).The following studies were done: 131 I uptake and thyroid scan, serum thyroxine, triiodothyronine and thyrothrophic hormone levels, triiodothyronine resin uptake, thyroxine-binding globulin capacity, serum albumin concentration, antithyroglobulin and antimicrosomal complement-fixing antibodies, thyroid...

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