hook effect

Prolactinoma is the most common cause of pathologic hyperprolactinaemia. The tumour size usually correlates with the prolactin level. Extremely high prolactin levels might cause the hook effect, resolting in erroneously low readings. In patients with pituitary adenomas (≥ 3 cm) and normal to modestly elevated prolactin levels, a 100-fold sample dilution is required to eliminate the hook effect. ...