Aryl hydrocarbon receptor-interacting protein (AIP) is associated with 15-20% of 
familial isolated pituitary adenomas and 50-80% of cases with AIP mutation 
exhibit a somatotropinoma. Herein we report clinical characteristics of a large 
family where AIP R304X variants have been identified. AIP mutation analysis was 
performed on a large (n = 52) Turkish family across six generations. Sella MRIs 
of 30 family members were obtained. Basal pituitary hormone levels were 
evaluated in 13 family members harboring an AIP mutation. Thirteen of 52 family 
members (25%) were found to have a heterozygous nonsense germline R304X mutation 
in the AIP gene. Seven of the 13 mutation carriers (53.8%) had current or 
previous history of pituitary adenoma. Of these 7 mutation carriers, all but one 
had somatotropinoma/somatolactotropinoma (85.7% of the pituitary adenomas). Of 
the 6 acromegaly patients with AIP mutation (F/M: 3/3) the mean age at diagnosis 
of acromegaly was 32 ± 10.3 years while the mean age of symptom onset was 24.8 ± 
9.9 years. Three of the six (50%) acromegaly cases with AIP mutation within the 
family presented with a macroadenoma and none presented with gigantism. 
Biochemical disease control was achieved in 66.6% (4/6) of the mutation carriers 
with acromegaly after a mean follow-up period of 18.6 ± 17.6 years. Common 
phenotypic characteristics of familial pituitary adenoma or somatotropinoma due 
to AIP mutation vary between families or even between individuals within a 
family.