Transgenic overexpression of pituitary tumor-transforming gene (PTTG), the mammalian index securin, in early endocrine pituitary progenitor cells (using the promoter of αGSU, the α − subunit of the glycoprotein hormones TSH, LH, and FSH) leads to the eventual development of uni- or pluri-hormonal microadenomas (expressing LH alone, or LH with TSH and GH, respectively). This evidence concerns the gene PTTG1 and neoplasm.