Morphofunctional study of pituitary adenomas with acromegaly by immunoperoxidase technique and electron microscopy.

In attempting to establish a functional classification of acidophilic adenomas of the pituitary gland, immunoperoxidase staining techniques specific for growth hormone (GH), prolactin (PRL), and luteinizing hormone (LH) were carried out. Surgically removed specimens from 24 acromegalic patients were studied. The pathologic observations were then compared with the basal plasma levels of each of the hormones. The existence of GH was demonstrated in all patients. Immunohistologically, GH-secreting adenomas could be subdivided into three types: Type I had the highest plasma-GH level (average 121 ng/ml), while the average plasma-GH levels of types II and III were 103 ng/ml and 73 ng/ml, respectively. This result suggested that the serum-GH level may correlate with the GH cell population in a tumor. In 13 of the acromegalic patients, immunoenzyme methods were utilized in order to identify prolactin cells. No clear correlation between serum-PRL levels and the distribution of PRL cells could be demonstrated. A few immunoreactive LH cells were found in 13 patients. These LH cells may be a mixture of normal cells, based on our clinical finding.