GROWTH-HORMONE RESPONSES TO GROWTH HORMONE-RELEASING HORMONE, CLONIDINE AND INSULIN-INDUCED HYPOGLYCEMIA IN NORMAL WEIGHT BULIMIC WOMEN

The growth hormone (GH) responses to GH-releasing hormone (GHRH; 1 µg/kg BW in an i.v. bolus), clonidine (150 µg in a single oral dose) and insulin (0.15 IU/kg BW in an i.v. bolus) induced hypoglycemia were evaluated in 7 normal weight bulimic women with regular menstrual cycles and in 7 age- and weight-matched normal women. In addition, the effect of thyrotropin-releasing hormone (TRH; 200 µg in an i.v. bolus) on serum thyroidstimulating hormone (TSH) and GH levels was measured in the same subjects. Tests were carried out in random order on the 22nd days of the following menstrual cycles. A control test with the i.v. administration of normal saline instead of drugs was carried out 2 days after the TRH test. Basal GH levels were significantly higher in bulimic women than in normal controls; despite higher GH levels, bulimic women showed normal circulating concentrations of somatomedin-C (Sm-C). Serum GH levels remained unmodified during the control test. In contrast, the administration of GHRH, clonidine or insulin induced significant GH responses in all subjects. Bulimic and normal women showed comparable responses after GHRH, clonidine or hypoglycemia. The hypoglycemic response to insulin was similar in bulimic and control subjects. The administration of TRH was unable to increase the circulating levels of GH in the normal controls, whereas it significantly increased GH concentrations in 5 of 7 bulimic women. Delayed TSH responses to TRH were observed in the bulimic group. These data indicate that normal weight bulimia is not accompanied by abnormalities in the hypothalamic pituitary responsiveness to normally acting GH-releasing stimuli. Taken together with the finding of normal plasma Sm-C levels, these results suggest the integrity of the GHRH-GH-somatomedin axis in bulimia. On the other hand, the anomalous effects of TRH suggest an abnormal sensitivity of the GH and TSH secretory systems to TRH in bulimia. © 1990 S. Karger AG, Basel.