BIPSS is performed in patients of ACTH-dependent CS when there are discordant responses to dynamic testing (intravenous CRH stimulation and HDDST (high-dose dexamethasone suppression test)) or pituitary imaging fails to localize adenoma or reveals pituitary tumor with size ≤6 mm (12, 19, 20, 21, 22). This evidence concerns the gene CRH and pituitary tumor.