The most common disorder in endocrinology with weight loss and lack of energy is hyperthyroidism. In some cases of hyperthyroidism, there is persistent weight loss and weakness due to too much consumption and high metabolism in the body. Another cause malignant tumors, such as stomach cancer, intestinal cancer or liver cancer, these cases may have weight loss and weakness. In these cases, we need to go to the hospital to see if the cause is pathologic. It is better to combine the opinions of gastroenterologists and endocrinologists, complete the relevant examinations, and synthesize the opinions of the above physicians to see what causes weight loss with generalized fatigue. The above content is for reference only, specific medication, treatment, please refer to the doctor’s guidance.