To clarify whether adrenal gland secretes
inhibin in vivo in physiological or pathological conditions, we measured the levels of
inhibin-like immunoreactivity (
inhibin-LI) in adrenal veins (A-vein) and compared them with those in inferior vena cava (IVC) using blood samples obtained at catheterization of adrenal vein in the patients with adrenal
adenoma manifesting
Cushing's syndrome (Cs),
aldosterone-producing
adenoma, clinically non-functioning
adenoma and normal adrenal gland. The
tumor sides of A-veins in the patients with
adenomas and also both sides of A-veins in subjects with normal adrenal glands showed significantly higher contents of
inhibin-LI than their IVC. When the
inhibin-LI secretion rate from adrenal gland was estimated by the difference between the levels of A-vein (
tumor side) and IVC, Cs
adenomas showed the highest secretion rate. Similarly, the tissue
inhibin-LI content and the basal secretion rate of inhibit-LI from primary cultured cells were the highest in Cs
adenomas. These findings indicated that normal adrenal glands and
adrenocortical adenomas produced and secreted
inhibin-LI into the general circulation in vivo and Cs
adenomas have relatively high capacity for secreting
inhibin-LI, and the present study provided the first in vivo evidence for adrenal
inhibin-LI production in pathological conditions.