Altered pituitary–thyroid (PT) function (TSH, FT4, FT3 plasma levels) was correlated with symptoms of Eating Disorders (ED) in 137 patients (65 ANR, 12 ANP, 19 ANBP, 26 BN, 8 EDNOS-AN, 7 EDNOS-BN) and 30 controls. PT hormone concentrations were assessed by immunofluorimetry and psychopathology by EDI-2 and HSCL-90. Values of TSH were decreased in ANP, BN, EDNOS-AN, of T4 in ANR, ANP, AN-BP, of T3 in ANR, ANP, ANBP, BN, EDNOS-AN, EDNOS-BN. TSH values correlated negatively with ineffectiveness in BN and EDNOS-AN, and with depression in EDNOS-AN. FT4 values correlated positively with perfectionism in ANR, ANP and ANBP, with interoceptive awareness in EDNOS-AN, and negatively with depression in EDNOS-AN and with body dissatisfaction in EDNOS-BN. FT3 values correlated positively with perfectionism in ANBP and BN, with ineffectiveness in ANR and ANP, with depression in EDNOS-AN, with hostility in ANR and EDNOS-BN, with interpersonal sensibility in ANP, with somatization in EDNOS-BN, and negatively with interpersonal distrust in EDNOS-AN. Prospective studies are needed to confirm whether or not altered PT parameters correlate with ED symptoms during the course of the diseases.