Growth hormone (GH) deficiency in acromegaly: significance of GH stimulatory tests in relation to the twenty-four hour GH secretion

A. A. van der Klaauw; A. M. Pereira; S. W. van Thiel; J. W. A. Smit; E. P. M. Corssmit; N. R. Biermasz; M. Frolich; A. Iranmanesh; J. D. Veldhuis; F. Roelfsema; J. A. Romijn

doi:10.1055/s-2006-932936

Experimental and Clinical Endocrinology & Diabetes, Table of Contents

Growth hormone (GH) deficiency in acromegaly: significance of GH stimulatory tests in relation to the twenty-four hour GH secretion

AA van der Klaauw ¹, AM Pereira ¹, SW van Thiel ¹, JWA Smit ¹, EPM Corssmit ¹, NR Biermasz ¹, M Frolich ², A Iranmanesh ³, JD Veldhuis ⁴, F Roelfsema ¹, JA Romijn ¹

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

Abstract

Aims: Radiation therapy for pituitary adenomas frequently leads to growth hormone (GH) deficiency. Whether radiation in acromegaly, due to a GH-secreting pituitary adenoma, induces a comparable change in GH secretion is not known.

Hypothesis: In the long-term, stimulated and spontaneous GH release cannot be distinguished in patients irradiated for acromegaly or other pituitary adenomas.

Design/subjects: Ten acromegalic patients and 10 patients with other pituitary adenomas were investigated. Mean time after radiation was 17 and 18.7 years, respectively. Stimulated GH release was evaluated by infusion of insulin (Insulin Tolerance Test (ITT)), GHRH, GHRH-arginine and arginine, and spontaneous GH by 10 minutes blood sampling for 24h. Analyses were by Cluster and approximate entropy.

Outcomes: No group differences existed in stimulated GH concentrations in any test, and the maximal GH concentration by ITT was below 3µg/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 2 acromegalic and 3 non-acromegalic patients. IGF-I was below 2 SD-score in 9 patients in each group.

Conclusion: Irradiation in acromegaly leads to loss of GH responses to various stimuli and diminished spontaneous release. These outcomes are indistinguishable from those of GH deficiency associated with other irradiated pituitary disorders.