Transcriptional regulation of pituitary gonadotrophin subunit genes.

The gonadotrophic hormones, LH and FSH, are synthesized in and secreted from gonadotroph cells in the anterior pituitary and comprise a common alpha-subunit and a hormone-specific beta-subunit. Gonadotrophic gene expression is activated during embryogenesis, independent of GnRH stimulation and increases as GnRH output increases, reaching adult levels at puberty. The transcriptional regulation of pituitary gonadotrophin subunit gene expression is regulated by two types of transcription factor: those that restrict and direct gene expression to gonadotrophs and those that modulate GnRH-regulated gene expression. Synergism between these two types of factor ensures gonadotroph-specific GnRH-regulated gene expression. It is not known whether these two types of transcription factor are mutually exclusive or whether they have overlapping functions. GnRH-regulated gonadotrophin subunit gene expression is modulated by transcription factors controlled by a complex interaction of GnRH, steroids and gonadal peptides, all of which bind to receptors that activate disparate intracellular signalling pathways. It remains to be established how these signalling pathways interact to transduce specific transcriptional activation of common alpha-subunit and LH and FSH beta-subunit gene expression.