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垂体前叶五类细胞的功能特化受普遍存在和细胞特异性转录因子的控制。细胞特异性转录因子Ｐｉｔ－１对生长激素（ＧＨ）、泌乳素（ＰＲＬ）基因的基础表达和对促甲状腺激素（ＴＳＨ）β－亚基基因的调节表达是必要的。转录因子截然不同的结合位点和某些转录控制机制，清楚地显示出以ＴＳＨ基因为例的垂体激素基因表达调节的复杂性。人Ｐｉｔ－１基因的不同突变证实，这个蛋白质的作用与以ＧＨ、ＰＲＬ和ＴＳＨ缺陷为特征的联合性垂体激素缺陷有关
Functionalization of the five pituitary cells is controlled by ubiquitous and cell-specific transcription factors. The cell-specific transcription factor Pit-1 is essential for the basal expression of the growth hormone (GH), prolactin (PRL) genes and the regulatory expression of the thyroid stimulating hormone (TSH) β-subunit gene. The distinctly different binding sites of transcription factors and some transcriptional control mechanisms clearly show the complexity of regulation of pituitary hormone gene expression, exemplified by the TSH gene. Different mutations in the human Pit-1 gene confirm that the role of this protein is associated with defects in the combined pituitary hormone characterized by defects in GH, PRL and TSH