What does a pregnancy test measure for?

A pregnancy test specifically measures the presence of human chorionic gonadotropin (hCG) in a person's urine or blood. hCG is a hormone produced by the placenta shortly after a fertilized egg attaches to the uterine lining. This hormone can typically be detected in the blood or urine as early as a week after conception, making it a reliable indicator of pregnancy.

While estrogen and progesterone play vital roles in maintaining pregnancy and preparing the body for it, they are not the hormones primarily tested for in standard pregnancy tests. Insulin is unrelated to pregnancy testing as it regulates blood sugar levels instead of serving as a marker for pregnancy. Therefore, detecting hCG is critical for confirming pregnancy.