It’s well established that women undergo a monthly menstrual cycle that includes fluctuations in hormones, and eventually a cease to these cycles at menopause. While there are numerous jokes about male “manstruation” and “manopause,” mental_floss spoke with two experts in male endocrinology and fertility—Paul Marshburn, a reproductive endocrinologist at Carolinas HealthCare System in North Carolina, and Brad Anawalt, an endocrinologist and chief of medicine at University of Washington Medical Center—to answer the question: Do men undergo a similar hormone cycle?

Despite one researcher’s controversial theory that men do have a monthly cycle (his results were never replicated), the short answer is almost certainly no, men do not experience a cyclical hormone shift on a monthly basis. Instead, they experience a daily (or diurnal) rise and fall of the most prominent hormone in their bodies, testosterone (T). While male bodies also produce a form of estrogen called estradiol (largely through a process that converts testosterone into estradiol), testosterone is either directly or indirectly the key to many health functions in their bodies, responsible for regulating sex drive (libido), bone mass, fat distribution, muscle mass and strength, and producing red blood cells and sperm. For men in good to average health, testosterone levels are highest in the morning hours, which cause morning erections, and increased energy and vitality. Testosterone levels then slowly drop as the day goes on and are at their lowest at the end of the day and evening. Because of this, men should get blood testosterone levels checked in the morning hours for an accurate baseline.

Certain activities can cause fleeting spikes of testosterone during the day, such as intense exercise or sexual activity. Likewise, stress and illness can cause sudden drops in testosterone in a given day. Levels also decline naturally over the course of a man’s life as he ages; his testosterone levels begin to drop as early as age 30 between 0.5 and one percent below his baseline per year.

Other causes for drops in testosterone include illness, from the seasonal flu to significant diseases like diabetes or cancer, since the body’s need to conserve energy often reduces the need to produce sperm or have sex. Some research points to seasonal sources of spikes and surges in testosterone, particularly in countries that experience longer than usual light and dark cycles, like Finland or Norway, where testosterone levels bottom out in summer and reach a high in late fall. Eating disorders and lack of sleep can also effect testosterone levels and sperm production.

Testosterone therapy to replace normal, age-related declines is a growing area of treatment. The research body on this is small, but a 2016 New England Journal of Medicine study found conclusively that testosterone therapy in men ages 65 and over improved sexual function and libido.

Loss of testosterone leads to a reduction in sexual arousal, decreased ability to achieve an erection, and loss of muscle mass and tone and bone marrow and density. More research has also found that low estradiol levels in aging men may be linked to cardiovascular disease and heart failure.

Ultimately, the best way for men to keep their testosterone at normal levels is to engage in healthy lifestyle behaviors such as exercise and healthy eating, and to keep to a minimum opioid medications, alcohol and smoking.