Some NETs release hormones, which can cause a lot of disruptive symptoms. When a NET produces hormones, it is called a “functional” neuroendocrine tumor. When a NET does not produce hormones, it is called “nonfunctional.”
Nonfunctional and functional tumors are generally associated with gastrointestinal (GI), pancreatic, and lung NETs. Testing can help determine whether a tumor is functional or nonfunctional.