Reverse Transcription Polymerase Chain Reaction Analysis of Pituitary Hormone, Pit-1 and Steroidogenic Factor-1 Messenger RNA Expression in Pituitary Tumors

Pit-1 is a transcription factor that appears early in embryonic pituitary gland formation and is necessary for the development of somatotropes, lactotropes and thyrotropes. Steroidogenic factor-1 (SF-1) is another early appearing transcription factor that is involved in the development of gonadotropes. In this study we have compared RT-PCR analysis of hormone mRNA with traditional IHC for classification of 27 pituitary tumors and have evaluated the correlation of Pit-1 and SF-1 mRNA with hormone mRNA. RT-PCR detected concordant hormone mRNA in 100% of GH IHC positive, 100% of PRL IHC positive, 33% of TSH IHC positive, and 93% of gonadotropin IHC positive tumors. IHC, however, was concordant in only 71% of GH mRNA positive, 78% of PRL mRNA positive, 17% of TSHβ mRNA positive, and 76% of FSHβ mRNA positive tumors. Pit-1 mRNA was positive in 87% of tumors in which mRNA for GH, PRL or TSHβ was detected and in only 17% of GH, PRL and TSHβ mRNA negative tumors. SF-1 mRNA was positive in 94% of tumors in which mRNA for FSHβ was present and in no FSHβ mRNA negative tumors. We conclude that RT-PCR analysis of hormone mRNA may be more sensitive than traditional hormone IHC for classification of pituitary tumors. Furthermore, tumor Pit-1 mRNA positively correlates with GH, PRL and TSHβ mRNA while tumor SF-1 mRNA correlates well with FSHβ mRNA. Combined analysis of hormone and transcription factor mRNA in pituitary tumor tissue may therefore be a more meaningful approach to pituitary tumor characterization.