Lack of somatostatin analogs effectiveness in gonadotropin-secreting pituitary adenomas: Report of a case and review of the literature

Gonadotropin-secreting pituitary adenomas are rare. Surgery remains the treatment of choice, whereas medical therapy is used when surgery has failed, is contraindicated, or is refused. Recently, data suggest a possible inhibitory effect of somatostatin analogs (SSAs) in these adenomas and their overall effectiveness is controversial. Moreover, although a subset of gonadotropinomas is partially responsive to SSAs in terms of hormone inhibition, SSA efficacy on tumor shrinkage is less clear. We report the case of a 55-year-old patient, with a pituitary mass of 55 × 47 mm, with high levels of alpha-subunit (7.2 U/L) and follicle-stimulating hormone (FSH) (67.7 U/L). Before surgery, octreotide LAR (20 mg intramuscularly every 28 days) was administered for 3 months. An OctreoScan revealed significant tumor uptake, but serum FSH, alpha-subunit levels, and tumor size were not decreased. Tumor specimens were studied by immunohistochemistry and by reverse transcriptase-polymerase chain reaction (RT-PCR). The adenomatous cells expressed SSTR subtype sst2A, agreeing with the OctreoScan result. RT-PCR analysis confirmed selective expression of sst2A as well as sst1 mRNAs. This report shows that in patients with a gonadotropinoma, responsiveness to an SSA is not always predicted by scintigraphy, and in vitro expression of SSTRs may be dissociated from the in vivo response to SSAs in terms of hormone secretion and tumor growth. On the basis of this case, we reviewed the literature on this subject and analyzed it in this report.