Mutations in the pituitary-specific paired-like homeodomain transcription factor PROP-1 result in combined pituitary hormone deficiency (CPHD) which includes all anterior pituitary hormones with the exception of ACTH. In an inbred pedigree with CPHD, direct sequencing of the PROP-1 gene revealed a deletion of two base pairs (301-302delAG) in exon 2, resulting in a frameshift and a premature stop in codon 109 in the homeodomain. The clinical characteristics of this family support the notion that this truncation results in a more severe phenotype than missense mutations in the aminoterminal part of the homeodomain.