Homeobox genes are a group of transcription factors characterized by a homeodomain that initiates gene expression which regulates cell differentiation and development when it binds to a target promoter.
Molecular-genetic analysis of craniates reveals that, compared to less complex animals, they developed duplicate sets of many gene families that are involved in cell signaling, transcription, and morphogenesis (see homeobox).
Some of the identifiable causes are deficiency of pituitary growth hormone and/or gonadotropins, mild degrees of androgen insensitivity, a variety of genetic syndromes, and variations in certain homeobox genes.