Analysis of thyrotropin-releasing hormone-signaling components in pituitary adenomas of patients with acromegaly

Investigation of responsiveness to thyrotropin-releasing hormone in growth hormone-producing pituitary adenomas

Objective. The aim of this study was to investigate how the paradoxical response of GH secretion to TRH changes according to tumor volumes. Methods. Patients with newly diagnosed acromegaly were classified as either TRH responders or nonresponders according to the results of a TRH stimulation test (TST), and their clinical characteristics were compared according to responsiveness to TRH and tumor volumes. Results. A total of 41 acromegalic patients who underwent the TST were included in this study. Between TRH responders and nonresponders, basal GH, IGF-I levels, peak GH levels, and tumor volume were not significantly different, but the between-group difference of GH levels remained near significant over the entire TST time. ΔGHmax-min during the TST were significantly different according to the responsiveness to TRH. Peak GH levels and ΔGHmax-min during the TST showed significantly positive correlations with tumor volume with higher levels in macroadenomas than in microadenomas. GH levels over the entire TST time also remained significantly higher in macroadenomas than in microadenomas. Conclusion. Our data demonstrated that the paradoxical response of GH secretion to TRH in GH-producing pituitary adenomas was not inversely correlated with tumor volumes.

Growth hormone measurements in the diagnosis and monitoring of acromegaly

Before the availability of immunoassays for IGF-I, growth hormone (GH) measurement was the sole method used in the biochemical assessment of acromegaly. IGF-I has since been established as the most reliable biochemical indicator of acromegaly. The last 25 years has seen important advances in the understanding of the neuroregulation and in the characterization of GH secretion in acromegaly. The availability of supersensitive GH has changed many aspects of the interpretation of GH-value in the management of acromegaly. Hypersecretion and abnormal neuroregulation characterize GH secretion in acromegaly. GH can be measured in many ways: as a single random sample, as multiple samples, either spontaneously or as an integral part of a dynamic test. These approaches give useful information on diagnosis, therapy, and prognosis. There is a place for measuring GH in the management of acromegaly although it complements that of IGF-I.