Kisspeptins are neuropeptides which activate the hypothalamo-pituitary gonadal axis and are considered to play important physiological roles in the reproduction. Kisspeptins have also been reported to stimulate the aldosterone secretion from the adrenal cortex. However, the expression of kisspeptins in human adrenal glands and adrenal tumors has not been clarified yet. We, therefore, studied the presence of kisspeptin-like immunoreactivity (LI) in human adrenal glands and adrenal tumors (adrenocortical adenomas, adrenocortical carcinomas, and pheochromocytomas) by radioimmunoassay and immunocytochemistry. Kisspeptin-LI was detected in all the tissues examined; normal portions of adrenal glands (3.0 +/- 2.3 pmol/g wet weight, n = 21, mean +/- SD), aldosterone-producing adenomas (4.6 +/- 3.3 pmol/g wet weight, n = 10), cortisol-producing adenomas (2.7 +/- 1.4 pmol/g wet weight, n = 14), adrenocortical carcinomas (1.7 +/- 0.2 pmol/g wet weight, n = 4), and pheochromocytomas (1.8 +/- 0.8 pmol/g wet weight, n = 6). There was no significant difference in kisspeptin-LI levels among them. Immunocytochemistry showed positive kisspeptin-immunostaining in normal adrenal glands, with stronger immunostaining found in the medulla. Furthermore, positive kisspeptin-immunostaining was found in all types of adrenal tumors examined; adrenocortical adenomas, adrenocortical carcinomas, and pheochromocytomas. The intensity of kisspeptin-immunostaining in these adrenal tumors was, however, not so strong as that in normal adrenal medulla. The present study has shown for the first time the presence of kisspeptin-LI in adrenal glands and adrenal tumors.