Although iatrogenic hypoprolactinemia is by far the most common reason for this disorder, low prolactin levels may be also secondary to genetically determined defects of its production or may be one of the manifestations of other pituitary disorders, including pituitary tumors, infiltrative diseases, hypophysitis, extensive pituitary surgery, massive cerebral trauma, pituitary ischemia or hemorrhage, high-dose radiotherapy, or chemotherapy [1]. The gene discussed is PRL; the disease is hypophysitis.