There are two types of lung cancer: 1) small cell lung cancer; and 2) non-small cell lung cancer. And within those two types are many different subtypes. I have small cell neuroendocrine carcinoma. Neuroendocrine tumors can be very tricky because they secrete excess hormones. In my case, the tumors secrete excess anti-diuretic hormone, which causes me to retain water, which causes my sodium level to plummet – a condition known as Syndrome of Inappropriate Antidiuretic Hormone (SIADH).