PRL and pituitary tumor: The activation of D2 receptor with DAs has been demonstrated to be an effective mechanism for inhibiting pituitary hormones, mainly PRL, GH, TSH, and ACTH, secretion in rodent and human pituitary tumour primary cultures and cell lines [23, 61, 76–80], and for inhibiting proliferation and/or inducing apoptosis in rodent and human lactotroph, somatotroph, corticotroph and non-functional pituitary tumour primary cultures and/or cell lines [81–84].