MEN1 patients also develop multiple parathyroid tumors, and subtotal parathyroidectomy has resulted in persistent or recurrent hypercalcaemia within 10 years in 20–60% of MEN1 patients, as opposed to ∼4% in non-MEN1 patients (Brandi et al., 2001; Schreinemakers et al., 2011; Waldmann et al., 2010). Here, MEN1 is linked to Hypercalcemia.