The cause of posterior pituitary ectopia associated with anterior pituitary hormone deficiencies is unknown. We describe children with combined pituitary hormone deficiency (CPHD) or isolated GH deficiency. In all cases, magnetic resonance imaging examination revealed abnormal pituitary gland development featuring ectopic posterior lobe location and frequently hypoplastic anterior lobes. Embryonic development of the pituitary requires the coordinated expression of specific transcription factors. Mutations of the PIT-1 and PROP-1 transcription factors are responsible for CPHD in some patients with normally positioned posterior pituitaries. In mice, the Lhx3 LIM homeodomain transcription factor is required for both structural development and cellular differentiation of the pituitary gland. Thus, we hypothesized that mutations in one or both of the two human LHX3 isoforms are responsible for posterior pituitary ectopia associated with anterior pituitary hypopituitarism. Comprehensive molecular analysis of the LHX3 isoforms was performed to test this hypothesis. No loss of function mutations in the LHX3 gene were detected. In addition, analysis of PROP-1 did not reveal mutations that might cause this phenotype. These studies suggest that the abnormal processes leading to the development of CPHD or GH deficiency associated with posterior pituitary ectopia are not a result of aberrant LHX3 or PROP- 1 function, but may be caused by defects at other gene loci.