The enrichment of some germline PRLR variants (e.g. Glu376Gln and Asn492Ile) (Table 1) in patients with prolactinomas, together with our previous observation that individuals harboring a loss-of-function mutant Arg188His PRLR developed hyperprolactinemia (25), led us to hypothesize that asymptomatic, healthy (i.e. normal) individuals with such PRLR variants may have alterations in serum prolactin concentrations. Here, PRLR is linked to hyperprolactinemia.