Endocrine Abstracts (2006) 11 P472

Stimulated and spontaneous growth hormone release in irradiated acromegalic patients

AA van der Klaauw1, AM Pereira1, SW van Thiel1, JWA Smit1, EPM Corssmit1, NR Biermasz1, M Frohlich4, A Iranmanesh2, JD Veldhuis3, F Roelfsema1 & JA Romijn1

1Leiden University Medical Center, Department of Endocrinology and Metabolism, Leiden, Netherlands; 2Salems Veterans Affairs Medical Center, Endocrine Service, Research and Development, Salem, Virginia, United States; 3Endocrine Research Unit, Department of Internal Medicine, Mayo School of Graduate Medical Education, General Clinical Research Center, Rochester, Minnesota, United States; 4Leiden University Medical Center, Department of Clinical Chemistry, Leiden, Netherlands.

Growth hormone deficiency frequently occurs as consequence of radiation therapy in pituitary disorders. However, it not known whether radiation therapy in acromegaly results in comparable diminution of GH secretion. We therefore hypothesized that stimulated and spontaneous GH release is ultimately indistinguishable in irradiated acromegalic patients and irradiated patients with other pituitary disorders. For this study 10 acromegalic patients and 10 patients with other pituitary disorders (8 patients with NFA and 2 with Cushing’s disease) were investigated. Mean time after radiation treatment was 17 and 18.7 years, respectively. Stimulated GH was evaluated by insulin tolerance test (ITT), GHRH, GHRH-arginine and arginine tests and spontaneous GH by measuring blood samples obtained at 10 min intervals during 24 h. The 24 h profiles were analyzed with Cluster and approximate entropy. No group differences in stimulated GH concentrations in any test were found. Maximal GH concentration by ITT was below 3 μg/L in all patients, compatible with severe GH deficiency. Spontaneous GH secretion was similar in both patient groups, including basal release, pulsatility and regularity. Pulsatile secretion was lost in two acromegalic patients and in 3 patients of the control group. IGF-I was below 2 SD-score in 9 patients of either group. We conclude that irradiation in acromegaly finally leads to loss of normal GH response to various stimuli and to diminished spontaneous release. The stimulated and spontaneous GH patterns are indistinguishable from those of GH deficiency patients encountered in other irradiated pituitary disorders.