INS and hyperprolactinemia: The final effect of PRL on insulin secretion/sensitivity, however, is believed to depend on its concentration: while higher levels of PRL within physiological concentrations (such as what occurs in pregnancy and puerperium) are associated with improved insulin sensitivity and glucose metabolism and lower prevalence of MS (37, 38), severe hyperprolactinemia (seen in pathological states such as prolactinomas) is associated with insulin resistance due to downregulation of insulin receptors (39).