A man’s lack of energy and fatigue may be due to physiological reasons, but also due to hypothyroidism, cancer and other pathological reasons. 1. Physiological reasons: long-term sleep deprivation of the male population, may be due to the body for a long time without adequate rest, the phenomenon of lack of energy and fatigue. 2. Pathological causes (1) Hypothyroidism: male patients with hypothyroidism may suffer from insufficient synthesis and secretion of thyroid hormones, resulting in slow metabolism, which leads to the phenomenon of lack of energy and fatigue. (3) Cancer: Cancer cells can affect the physiological activities of normal cells by changing the microenvironment, and some cancer patients may have a lack of energy and fatigue in the early stage of the disease. Compared with normal fatigue, cancer fatigue is generally heavier and lasts longer, and it cannot be relieved by rest. Lack of energy and fatigue can also be caused by other diseases, and men who have this phenomenon are recommended to consult a doctor in time to get a clear diagnosis and follow the doctor’s instructions for treatment.