25 g of sodium is secreted into the gut

 Sodium Each day, about 25 g of sodium is secreted into the gut, and a further 5 g is ingested with food: this total of 30 g represents about 15% of the total body sodium. Active sodium resorption occurs in the upper jejunum, w

Cancers of lung, breast, and head and neck are the ones most commonly associated with hyponatremia, which is predominantly of the SIADH type. Among these cancers, lung cancer has the lowest survival, the overall rate being only 9%–13% in comparison to 80% and 50% for breast and head and neck cancer, respectively.

Doctors may prescribe a vasopressin receptor antagonist. Vasopressin is a hormone that tightens blood vessels and increases water reabsorption in the kidneys. These medicines help the kidneys to remove large amounts of urine to reduce excess water without reducing sodium.

Small-cell lung cancer tumors are made up of neuroendocrine cells – the same kind of cells that release hormones. In the case of SIADH, cancer cells release ADH, causing a spike in levels of this hormone. Unlike ADH release controlled by the pituitary, ADH released from cancer cells is not suppressed by low sodium levels or normal blood volume. That’s what makes cancer-related ADH release inappropriate.