A 37-year-old pregnant woman developed continuous headache in the 10th week of pregnancy, followed by bilateral visual field defect and general malaise in the 24th week. The brain magnetic resonance imaging showed a pituitary mass. In laboratory examination, plasma concentration of free thyroxine, thyroid stimulating hormone (TSH), cortisol, and adrenocorticotropic hormone (ACTH) was low. General malaise vanished shortly after the replacement therapy of glucocorticoid and thyroid hormone, but partial central diabetes insipidus (CDI) appeared, which could be treated with desmopressin acetate (DDAVP). The visual field defect having enlarged, transsphenoidal surgery was performed in the 31st week of pregnancy. Adenohypophysis could be resected, and it showed infiltration of mature lymphocytes. After the surgery, the visual defect had improved, but hormone replacement was still necessary. She delivered a baby in the 38th week without any trouble. Provocative tests after delivery revealed a low response in TSH, prolactin (PRL), and follicle stimulating hormone (FSH). Hormone replacement and DDAVP administration was necessary in the same doses after delivery. The diagnosis was lymphocytic panhypophysitis (LPH). In the case of pregnant woman, LPH should be included in the differential diagnosis of pituitary mass for the fetomaternal safety.