Mendelian randomization: loosening the Gordian knot of testosterone and male ageing

It is unknown whether the reduced blood testosterone among unselected older men (andropause'') compared to healthy younger men is due to ageing per se or as a non-specific adaptive reaction to chronic diseases accumulating during ageing. A new data analytical technique, Mendelian Randomisation, sheds light on this issue by suggesting that male ageing does not significantly cause lowering of blood testosterone. This shifts the focus from whether treatment of andropause is justified to whether testosterone is safe and effective treatment for the major co-morbidities of ageing such as cardiovascular disease, obesity and chronic organ failure syndromes.