Effects of acute hyperglycemia on mental efficiency and counterregulatory hormones in adolescents with insulin-dependent diabetes mellitus.

OBJECTIVE: To determine whether acute hyperglycemia adversely affects mental efficiency to the same extent as acute mild hypoglycemia. STUDY DESIGN: We administered a battery of cognitive tests to adolescents studied at hyperglycemic (20 mmol/L (360 mg/dl)), hypoglycemic (3.3 mmol/L (60 mg/dl)), or euglycemic (5.5 mmol/L (100 mg/dl)) targets, which were maintained by an insulin-glucose clamp. The study included 36 children, 9 to 19 years of age (mean = 14.7 years), with diabetes duration more than 2 years (mean = 6.9 years). RESULTS: Cognitive test performance did not deteriorate during hyperglycemia. In contrast, there was a significant decline in performance on all cognitive tests during mild hypoglycemia. Autonomic symptoms did not change significantly during hyperglycemia or during the rapid return from hyperglycemia to euglycemia. Although significant increments in epinephrine and pancreatic polypeptide levels occurred during mild hypoglycemia, no changes in counterregulatory hormones occurred during hyperglycemia. An exploratory regression analysis demonstrated that changes in mental efficiency were best predicted by increases in pancreatic polypeptide, a marker of autonomic activation. CONCLUSION: These results confirm our previous finding that mild hypoglycemia causes transient decrements in cognitive function. In contrast, neither hyperglycemia, nor the rapid drop from acute hyperglycemia to euglycemia, affected symptoms, cognitive function, or counterregulatory hormone secretion.

Mild hypoglycemia associated with deterioration of mental efficiency in children with insulin-dependent diabetes mellitus.

To assess the effects of mild hypoglycemia on cognitive functioning in diabetic children, we used an insulin glucose clamp technique to induce and maintain a hypoglycemic state. Eleven patients, 11 to 18 years of age, completed a series of cognitive tests during a baseline euglycemic state (100 mg/dl (5.5 mmol/L] and repeated those measures at the beginning and end of a hypoglycemic plateau (55 to 65 mg/dl (3.1 to 3.6 mmol/L], and again at restoration of euglycemia. At plasma glucose levels of 60 to 65 mg/dl (3.3 to 3.6 mmol/L), a significant decline in mental efficiency was found. This was most apparent on measures of mental "flexibility" (Trial Making Test) and on measures that required planning and decision making, attention to detail, and rapid responding. Moreover, complete recovery of cognitive function was not contemporaneous with restoration of euglycemia, particularly on those tests requiring rapid responding and decision making (choice reaction time). Not all subjects showed evidence of cognitive impairment during hypoglycemia. The very high degree of intersubject variability suggests that, in addition to plasma glucose values, unknown physiologic variables are responsible for triggering cognitive impairments in school-aged youngsters with diabetes during an episode of mild hypoglycemia.

Reversible suprasellar pituitary mass secondary to hypothyroidism.

Sellar enlargement and suprasellar extension of a pituitary mass, demonstrated by magnetic resonance imaging or computed tomographic scanning in three children with primary hypothyroidism, resolved after treatment with levothyroxine sodium. This condition, a logical consequence of the pathogenesis of primary hypothyroidism, must be considered in patients with pituitary and suprasellar masses.