Weizmann study of 300 million lab tests finds menopause reshapes the body abruptly

Menopause has usually been described as a slow, gradual transition. A study led by Professor Uri Alon of the Weizmann Institute of Science, published in Nature Medicine on 12 October 2026, suggests that for much of the body it is closer to a step. Working with Dr. Glen Pridham and Yoav Hayut from Alon's lab, and with partners at Clalit Health Services, Kaplan Medical Center and Rabin Medical Center, the team analysed more than 300 million laboratory results from over a million women in Israel and the United States.

The data came from roughly two decades of Clalit medical records and from the long-running US National Health and Nutrition Examination Survey. Of 90 types of routine lab test, 52 showed abrupt shifts around the final menstrual period, including markers of bone health, liver and kidney function, blood chemistry and cholesterol. Iron and haemoglobin rose, probably because monthly bleeding stops. Men of the same ages showed no comparable jumps, and the pattern looked similar in both countries. Because medical records rarely note exactly when a woman's last period occurred, the researchers borrowed a sharpening technique inspired by the way astronomers clean up blurred telescope images.

The team also found that changes in sex hormones begin to accelerate more than a decade before menopause, several years earlier than previously believed. Women taking menopausal hormone therapy tended to show smaller jumps, especially in bone, liver and kidney markers, although the authors stress that an observational study cannot show the treatment caused the difference. Alon told Scientific American that oestrogen acts on receptors in almost every cell, which may explain why the effects reach so many organ systems at once.

The findings describe population averages and cannot predict when an individual woman will experience these changes, and some outside experts urged caution. Menopause specialists in Australia called the 'cliff' label alarming, pointed out that the study relied on existing records, and noted that a long-running US study had found changes to be more gradual. The researchers say the result opens a longer window for prevention, such as exercise and diet changes aimed at bone and heart health, and that the same method could be used to study other life transitions, including puberty, pregnancy and the onset of disease.