Germline mutations in the aryl hydrocarbon receptor-interacting protein gene 
(AIP) predispose to young-onset pituitary tumours, most often to GH- or 
prolactin-secreting adenomas, and most of these patients belong to familial 
isolated pituitary adenoma families. The molecular pathway initiated by the 
loss-of-function AIP mutations leading to pituitary tumour formation is unknown. 
AIP, a co-chaperone of heat-shock protein 90 and various nuclear receptors, 
belongs to the family of tetratricopeptide repeat (TPR)-containing proteins. It 
has three antiparallel α-helix motifs (TPR domains) that mediate the interaction 
of AIP with most of its partners. In this review, we summarise the known 
interactions of AIP described so far. The identification of AIP partners and the 
understanding of how AIP interacts with these proteins might help to explain the 
specific phenotype of the families with heterozygous AIP mutations, to gain 
deeper insight into the pathological process of pituitary tumour formation and 
to identify novel drug targets.