Background Pituitary apoplexy (PA) is an uncommon syndrome characterized by a sudden onset of headache, visual impairment and/or reduced conscious level caused by haemorrhage and/or infarction of the pituitary gland. We report a case of PA related to pregnancy and treatment with low molecular-weight heparin (LMWH) presented with sudden and severe headache and hypopituitarism. Clinical case A 33-year-old primigravid woman was admitted to the emergency department because a sudden onset of headache, nausea and photophobia. Her past medical history revealed: traumatic splenectomy in early childhood with portal hypertension secondary to portal thrombosis; digestive hemorrhage; late menarche (18 years old), with irregular menstrual cycles during the first years after menarche but normalized in the last five years. She was under treatment with carvedilol, spironolactone, and LMWH started at the time of pregnancy. On physical exam she was conscious, without cranial nerve paralysis and with severe photophobia. Her blood pressure was 80/60. A Brain Magnetic Resonance (MRI) showed a spontaneous hyperintense image of 5x4,5 mm on the T1 weighted within a diffuse enlargement pituitary gland in contact with the optic chiasm. A pituitary apoplexy was suspected, so immediate treatment with intravenous hydrocortisone was started. Secondary adrenal and hypothyroidism insufficiency were confirmed. Clinical improvement was evident in the following days, and an elective cesarean delivery was performed at 37 weeks of gestation. On MRI performed 6 weeks after delivery, pituitary gland showed an important reduction on cephalo-caudal diameter, and persistence of hypopituitarism: TSH 0.01 mU/l (0.35-4.94), FT4 18 pmol/l (9-19), Cortisol 2.1 mg/dl, ACTH 12 pg/ml (0-54) LH: 3.4 U/l FSH 5.5 U/l, Prolactin 46.9 ng/ml (5.2 - 26.5) IGF-1 68 ng/ml (115-284). The patient is currently healthy, under hormonal replacement. Conclusions Although PA is an uncommon event in pregnancy, it is important to highlight that if unrecognized it is potentially life-threatening for the mother and the fetus. Sudden headache is the most common symptom. So, it must be considered among the differential diagnosis with other causes. It usually occurs in a previously undiagnosed pituitary adenoma. Although we could not rule out an unknown previous macroadenoma in this patient, regular menses before pregnancy and the diffuse pituitary enlargement images on MRI make that possibility more unlikely. Anticoagulation therapy is a well recognized precipitating factor. Most of the patients will have deficiency of one or more anterior pituitary hormones at presentation. Deficit of ACTH is the most crucial, so treatment with glucocorticoids must be immediately started. Conservative management with a prompt replacement of deficient hormones especially glucocorticoids, is a well validated option in mild cases. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. s presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.