KL and pituitary gland adenoma: Interestingly, a study in patients with pituitary adenomas showed that there was expression of klotho in both GH-secreting and non-GH-producing adenomas; this expression of klotho, proven by immunohistochemistry, was higher in non-GH-secreting adenomas, suggesting that non-GH-secreting pituitary cells are capable of producing klotho.