PRL and hyperprolactinemia: 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.