In the evaluation of a 26-year-old patient with 4 months of secondary amenorrhea, you order serum prolactin and b-hCG assays. The pregnancy test is positive, and the prolactin comes back at 100 ng/mL (normal <25 ng/mL in this assay). This patient requires

There is a marked increase in levels of serum prolactin during gestation to over 10 times those values found in nonpregnant women. If this woman were not pregnant, the prolactin value could easily explain the amenorrhea and further evaluation of hyperprolactinemia would be necessary. The physiologic significance of increasing prolactin in pregnancy appears to involve preparation of the breasts for lactation.