Serum Alpha-Subunit Levels In Patients With Pituitary Adenomas

OBJECTIVE Mle investigated preoperative and postoperative serum alpha -subunit levels and the alpha -subunit response to TRH in patients with various types of pituitary tumour and correlated the data with histological findings in order to clarify the significance of alpha -subunit measurement in pituitary adenomas.PATIENTS We examined 59 patients with pituitary tun;ours (22 with GH cell adenomas, 30 with clinically nonfunctioning adenomas and seven with other tumours) treated at Toranomon Hospital between 1996 and 1998.RESULTS The basal alpha -subunit Level was supranormal in six out of 22 (27%) patients with a GH cell adenoma and in nine out of 30 (30%) patients with a nonfunctioning adenoma. A paradoxical alpha -subunit response to TRH was found in seven out of 22 (32%) patients with a GH cell adenoma. These seven patients also showed a paradoxical GH response to TRH administration. In addition, paradoxical response to TRH was found in eight out of 30 (27%) patients with a clinically nonfunctioning adenoma. In contrast, patients with other types of pituitary tumour showed neither a supranormal alpha -subunit level nor a paradoxical response to TRH. The supranormal a-subunit level and the abnormal response to TRH were normalized in both GH cell adenoma and nonfunctioning adenoma patients after successful surgery. immunohistochemical studies showed alpha -subunit positive cells in 51% of GH cell adenomas or nonfunctioning adenomas and there was a good concordance with the serum cu-subunit levels in both GH cell adenoma and nonfunctioning adenoma patients.CONCLUSIONS These findings suggest that supranormal serum cu-subunit levels are mainly due to hypersecretion by the tumour itself, while the paradoxical alpha -subunit response to TRH is an associated phenomenon in patients with a GH cell adenoma or nonfunctioning adenoma. The alpha -subunit level and the response to TRH may be useful indicators for assessing the operative outcome, especially in nonfunctioning adenoma patients who have no ether definite endocrine markers.