These cytokines carry messages that regulate other elements of the immune and endocrine systems. In high amounts, these cytokines can be toxic and lead to persistent fatigue. Interferon's and interleukin's are cytokines, natural cell proteins that are normally released by white blood cells in response to infection. These cytokines carry messages that regulate other elements of the immune and endocrine systems. In high amounts, these cytokines can be toxic and lead to persistent fatigue.
Tumor cells compete for nutrients, often at the expense of the normal cells' growth.
In addition to fatigue, weight loss and decreased appetite are common effects. Cancer treatments can cause reduced blood counts, which may lead to anemia, a blood disorder that occurs when there is not enough hemoglobin in the blood. Hemoglobin is a substance in the red blood cells that enable the blood to transport oxygen through the body. When the blood can not transport enough oxygen to the body, fatigue can result. This is a common condition in general, but may happen after radiation therapy to the lymph nodes in the neck.