ACTA ENDOCRINOLOGICA (BUC)

Prolonged target gland failure causes pituitary hyperplasia, but rarely, secondary hyperplasias develop into autonomous neoplasms. We report herein a rare example of gonadotroph adenoma arising in a patient with prolonged hypogonadism due to Klinefelter syndrome. A pituitary macroadenoma with suprasellar extension was discovered incidentally by magnetic resonance imaging (MRI), in search for the cause of chronic saliva retention. His pre-operative serum concentrations of both luteinizing hormone (LH) and mostly follicle-stimulating hormone (FSH) were distinctly higher than normal, as expected, but the levels decreased after complete removal of the tumor, suggesting partial secretion of gonadotropins by the tumor. The surgically removed tissue showed a typical pituitary adenoma with distinct immunoreactivity for FSH (intense, homogeneous) and LH (scattered). In the fragmented parts of adjacent gland tissue, no hormone producing cell hyperplasia or presence of gonadal deficiency cells were detectable. In conclusion, our case is the description of a rare example of gonadotropin producing pituitary adenoma (FSH and LH) with increased serum levels of both gonadotropins in a patient with untreated Klinefelter syndrome.