Data obtained by gene array and semi-quantitative RT-PCR showed an increase in the expression of Sp3 and CRSP9 (co-regulator of Sp1 transcription factor, subunit 9) in the adrenal adenomas or bilateral macronodular hyperplasias of patients with GIP-dependent Cushing's syndrome; they were, however, also increased in some patients with non-GIP-dependent cortisol-secreting adenomas or with ACTH-dependent Cushing's disease.
Using RT-PCR amplification and cDNA hybridization, the GIP receptor was found to be overexpressed in the adenoma tissue but not in the adjacent adrenal tissue.
Aberrant gastric inhibitory polypeptide (GIP) receptor expression in bilaterally hyperplastic adrenals or unilateral adrenal adenomas is a rare form of adrenal hyperfunction.