A 35 year old, previously well caucasian woman presented with an episode of loss of consciousness, 3 months after the delivery of her first child. The post partum period was complicated by significant post partum haemorrhage. Initial investigations showed blood glucose 1.8mmol/L (3.5-5.5), corrected calcium 3.66mmol/L (2.10-2.55) and a suppressed TSH <0.03mIU/L (0.4-4.0) with an elevated freeT4 44.8pmol/L (9.0-20.0) indicating severe hypoglycaemia, hypercalcaemia and thyrotoxicosis. She responded rapidly to intravenous fluids, glucocorticoids, zolendronic acid and anti thyroidal medication. Thyroid scintigraphy was consistent with thyroiditis. Baseline cortisol and ACTH were undetectable indicating secondary adrenocortical deficiency. An insulin tolerance test demonstrated lack of ACTH and cortisol response with an appropriate GH response indicating Isolated ACTH deficiency (IAD). MRI pituitary did not show features of Sheehan’s syndrome. On long term follow up, isolated ACTH deficiency was noted to be the only endocrine abnormality until she developed Graves’ disease four years later. Although hypercalcaemia in association with Addison’s disease aggravated by concomitant thyrotoxicosis has been described, IAD presenting with hypercalcaemia is a unique feature. The patient’s development of Graves’ disease on follow up indicates underlying autoimmune pathophysiology increasing the likelihood that her IAD was a consequence of postpartum autoimmune hypophysitis. The role of postpartum haemorrhage in development of IAD in our patient is uncertain.