CASR and medullary thyroid gland carcinoma: PHPT may also be part of genetic endocrine syndromes including 1/ Multiple endocrine neoplasia (MEN) syndromes, type I (PHPT, duodenopancreatic neuroendocrine tumors and/or pituitary adenomas, MEN1 gene mutation) (4), or type II (PHPT, medullary thyroid carcinoma and/or pheochromocytoma, RET proto-oncogene mutation) (5); 2/ Hereditary hyperparathyroidism-jaw tumor (HPT-JT) syndrome secondary to CDC73 mutation (also known as HRPT2) (3); and 3/ Inactive Calcium-sensing Receptor (CaSR) secondary to genetic disorders (AP2S1, GNA11, CASR mutations) or anti-CaSR antibodies (6, 7).