Divergence between growth hormone responses to insulin-induced hypoglycaemia and growth hormone-releasing hormone in patients with non-functioning pituitary macroadenomas and hyperprolactinaemia

Clinical Endocrinology
J A BeentjesR P Dullaart

Abstract

The GH responses to the insulin tolerance test (ITT) and growth hormone-releasing hormone (GHRH) may yield different results in patients with pituitary lesions. The GH responses to these stimuli were compared in patients with untreated non-functioning pituitary macroadenomas, who represent an important cause of GH deficiency. Analysis of peak GH to ITT and to 100 micrograms GHRH in relation to an elevated PRL level (> 200 mIU/l for males and > 600 mIU/l for females) as an indication of hypothalamic-pituitary dysregulation, as well as in relation to other anterior pituitary hormone deficiencies. A peak GH < 5 micrograms/l in either test indicated GH deficiency. Twenty females and 14 males (median age 52 (23-77) years) evaluated preoperatively in a university hospital setting. In the whole group the median peak GH to GHRH (3.6 (0.9-26.3) micrograms/l) was higher than to ITT (1.6 (0.2-7.8) micrograms/l, P < 0.001). This difference was seen only in 19 patients with concomitant hyperprolactinaemia (P < 0.001). When hyperprolactinaemia was present, an insufficient GH peak was demonstrated by ITT in 16 cases and by GHRH stimulation in 7 cases (P < 0.01). The frequency of an insufficient GH peak by ITT (13 cases) and by GHRH (14 cases)...Continue Reading

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