The secret of the difference between men and women against aging, heart disease and cancer Differences in the function of the genes of the sex chromosomes can affect the body's immune response, tumor growth and age-related cellular changes. New research shows that sex chromosomes play a role far beyond determining biological sex and actively influence how cells age, deal with stress on the heart and fight deadly tumors. We have been taught for decades that sex hormones, such as estrogen and testosterone, explain almost all the health differences between men and women. When women lived longer than men or men had heart attacks at a younger age, medicine almost always directly blamed hormones, but now a groundbreaking study published in the journal Science has overturned that assumption. A major review article co-authored by Dr. Dan Theodorescu of the University of Arizona Cancer Center and Dr. Dana B. Duval from the University of California in San Francisco, shows that the X (X) and Y (Y) chromosomes are involved in the onset of diseases independent of hormones. "The X and Y chromosomes are often seen simply as determining biological sex, but their role in human health is much broader," explains Dr. Teodorescu. Our research shows that these chromosomes carry genetic instructions that affect the way cells age and the body's defense against important diseases throughout life." How do sex chromosomes take the wheel? Gene copy number differences between XX and XY chromosomal arrangements deep inside human cells drive a silent lifelong program that affects disease risk. While hormone levels fluctuate wildly throughout life, your chromosomes are in almost every cell from birth to old age. This stable presence allows them to directly influence immune system signaling, metabolism and cell repair through epigenetic mechanisms.