I am (almost) 61, and had been experiencing a lack of interest over a period of several years. Well, about a year ago, I was diagnosed with a pituitary tumor (a benign tumor). These things typically increase the production of a hormone called prolactin which, in males, suppresses the production of testosterone and decreases libido. It is treated easily with medication, and I am going in soon for an MRI to see if the tumor is gone. Without getting into any of the gory details about whether or not my libido has improved (I'm not dragging the average down anymore), I'd suggest that any of you guys who have been experiencing a lack of interest go and get your prolactin levels checked.