The effect of diabetic nocturnal hyperglycemia upon HGH release in sleep was studied in five insulin-treated, stable, nonobese juvenile diabetics on eleven nights and compared to mean release in thirteen normal young men. All were studied by sleep polygraphy. Samples were drawn every twenty minutes from indwelling venous catheters without disturbing sleep. HGH was measured by RIA and plasma glucose concentration by O-toluidine. Despite hyperglycemia of 195-382 mg. per 100 ml. on nine out of eleven nights at the time of sleep HGH peak, the repetitive nightly pattern of HGH release in diabetics resembled those of normals. The diabetic group's mean HGH concentration during sleep was 4.0 ± 0.6 ng./ml. (± S.E.) and mean peak sleep HGH concentration was 11.2 ±: 1.3 ng./ml., which were not signicantly different from those of normals (3.4 ± 0.3 and 12.5 ± 1.4 ng./ml. ± S.E. respectively). Thus, diabetic hyperglycemia, similar to constant glucose infusion hyperglycemia in normals, does not result in suppression of HGH release in sleep. This indicates that hyperglycemia is not an important regulator of rhythmical HGH release in sleep and suggests a primary neural character of this rhythm. HGH release in sleep was not enhanced in treated juvenile diabetes.

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