Primary hyperparathyroidism was the initial clinical manifestation in the majority of MEN1 patients (n = 44, 64.7%), while 18 patients (26.5%) developed a neuroendocrine tumor (67% of them located in the pancreas), and 6 patients (8.8%) developed a pituitary adenoma as the first MEN1-related clinical manifestation. Here, MEN1 is linked to primary hyperparathyroidism.