Pituitary homeobox 1 (Ptx1; also known as Paired-like homeodomain transcription factor 1, Pituitary homeobox 1, or Hindlimb-expressed homeobox protein backfoot) is a nuclear transcription factor encoded by the Pitx1 (also known as Bft, Potx, Ptx1) gene in mouse. Ptx1 is reported to stimulate LHbeta gene promoter activity either alone or synergistically with the orphan nuclear receptor steroidogenic factor-1 (SF-1) and the early growth response gene 1 (Egr-1). Ptx1 is expressed in the hindlimb, but not the forelimb, of developing mouse embryos, and reduced hindlimb size and loss of hindlimb-specific features are seen in Pitx1-knockout mice.