Lactation requires the presence of estrogen, progesterone and prolactin, and the evaluation of galactorrhea includes an elicitation of the patient’s history for various medications or foods (methyldopa, opiates, anti-psychotics, serotonin reuptake inhibitors, as well as licorice and for behavioral causes (stress, and breast and chest wall stimulation), as well as evaluation for pregnancy, pituitary adenomas (with over production of prolactin or compression of the pituitary stalk), and hypothyroidism. This evidence concerns the gene PRL and hypothyroidism.