Multiple endocrine neoplasia type 1 in patients with recognized pituitary tumours of different types

We have investigated the prevalence of MEN 1 in patients with recognized pituitary adenomas. Since hyperparathyroidism is present in nearly 95-100% of patients with MEN 1 and frequently is the first condition to be identified, the study was limited to the identification of patients with hyperparathyroidism while the screening for gastroenteropancreatic (GEP) lesions was carried out in patients with both pituitary and parathyroid lesions.

Serum total and ionized calcium, phosphate and intact PTH 1-84 (EASIA) were measured in 166 patients (68 with non-functioning pituitary adenoma, 42 with prolactinoma, 35 with GH-secreting adenoma, 17-with ACTH-screening adenoma, 1 with TSH-secreting adenoma, 1 with FSH-secreting adenoma and 2 with an only alpha-subunit secreting adenoma) referred to our clinic from 1990 to 1996. Plasma gastrin, somatostatin, pancreatic polypeptide and vasoactive intestinal peptide were measured by RIA in patients with hyperparathyroidism.

Eight of 166 patients (4.8%) were found to have primary hyperparathyroidism and among these 2 also had a gastrinoma while there was no evidence of other GEP tumours. Considering the tumour type, 6 had prolactinoma (14.3%), 1 GH-secreting adenoma (2.8%) and 1 non-functioning adenoma (1.5%). In most patients the diagnosis of pituitary tumour was made several years before that of hyperparathyroidism (from 1 to 15 years) although 6 patients had previously suffered from urolithiasis and one had undergone gastric resections for recurrent peptic ulcers. One patient was identified as a MEN 1 gene carrier and 2 had relatives with signs and symptoms referable to parathyroid or GEP lesions.

The study shows a prevalence of 4.8% of primary hyperparathyroidism in unselected patients with known pituitary tumours similar to that reported in a previous study. By contrast, the prevalence of MEN 1 in patients with prolactinoma was definitely high (14.3%). In most patients the diagnosis of pituitary tumours was made several years before that of hyperparathyroidism. Although the patients were believed to harbour a sporadic pituitary tumour, most of them had had signs and/or symptoms referable to one or both of the other organs involved in MEN 1, often concomitantly with those of pituitary tumours. These data indicate that the diagnosis of MEN 1 syndrome is missed in a substantial proportion of patients with prolactinomas and therefore the screening of these patients for the syndrome is strongly recommended.