Diri et al. retrospectively investigated 114 women with Sheehan Syndrome and found that none of the patients with basal PRL levels < 4 ng/ml responded to TRH stimulation test, whereas all patients with basal PRL levels > 7.8 ng/ml showed an adequate response, defined as a doubling of basal PRL levels [59]. This evidence concerns the gene PRL and Sezary syndrome.