Endocrine system cancers are malignant tumors that occur in the glands responsible for producing and secreting hormones. Hormones are chemical messengers that coordinate activities throughout the body. Except for thyroid cancer and cancer of the gonads (ovaries in females and testes in males), endocrine system cancers are rare disorders and are usually treatable when caught early.

The glands of the endocrine system exist in many parts of the body and control many functions, such as growth, metabolism, digestion and blood pressure. Endocrine glands include the pituitary gland and hypothalamus in the brain, the thyroid and parathyroid glands in the neck and the adrenal glands over the kidneys. Certain cells in the pancreas may also develop endocrine cancers. Thyroid cancer is the most common non-reproductive organ endocrine cancer. The remaining endocrine cancers are quite rare.

Endocrine system cancers usually cause an endocrine gland to produce too little or too much of a hormone. The changes in these hormone levels may produce symptoms such as weight changes, fatigue or vision changes. The cause of most endocrine system cancers remains unknown. Even though there are some associated risk factors, most people who develop an endocrine cancer have no known risk factors.

The reproductive glands of the ovaries in women and testes in men may also develop cancer. These cancers are more common than othre types of endocrine system cancer.