Expression of leptin receptor isoforms and effects of leptin on the proliferation and hormonal secretion in human pituitary adenomas

Objective: To pursue whether leptin regulates anterior pituitary cells, we studied the ex vivo expression of several isoforms of the leptin receptor (OB-R) as well as the in vitro effects of leptin administration in human pituitary adenomas. Methods: OB-R mRNA expression and in vitro response to leptin were studied in 39 pituitary macroadenomas. Results: All 4 OB-R subtypes were expressed in most adenomas. The expression was significantly more pronounced in GH-secreting adenomas as compared to non-functioning tumor cells (p < 0.05). Leptin administration in vitro did not significantly influence cell proliferation or the secretion of GH, FSH, LH or alpha-subunit. Conclusions: ( 1) Several isoforms of the OB-R, including the signal transducing full-length receptor, are expressed in most human pituitary adenomas. ( 2) This expression ex vivo is not associated with significant effects of leptin in vitro. Copyright (C) 2004 S. Karger AG, Basel.