Particularly, excluding the known causes of hyperprolactinemia as pregnancy, lactation, hypothyroidism, and drugs, PRL values within 25 -100 μg/L could be a response to temporary stimuli, like stress, insulin-induced hypoglycemia, sexual arousal, intensive exercise training, and circadian peaks, which requires to the subject a metabolic adaptation (11). This evidence concerns the gene PRL and hypothyroidism.