Elevated plasma level of lipotropin revealing an occult carcinoid tumor with normal plasma adrenocorticotropin.

The increases in the level of plasma lipotropin (LPH) and in the LPH/ACTH ratio are considered diagnostic tools in ectopic ACTH syndrome. However, plasma ACTH is also elevated in this syndrome. We report a case of a small carcinoid tumor with an increase in both ACTH and LPH in plasma before surgery. Eight months after the tumoral resection, plasma LPH alone was increased again, whereas plasma ACTH and plasma and urinary cortisol remained normal in this apparently cured patient. This repeated abnormality was the only available feature that allowed successful removal of the occult tumoral residue.