Endocrine Abstracts

Introduction: Milk-alkali syndrome is characterized by the triad of hypercalcaemia, metabolic alkalosis, and acute kidney injury and occurs due to excessive use of elemental calcium. Despite the widespread use of proton pump inhibitors, it is the third most common cause of hypercalcaemia after primary hyperparathyroidism and malignancy.

Case presentation: A previously normocalcaemic 33-year-old patient presented at 34 weeks gestation, feeling non-specifically unwell. She was delivered by emergency caesarean section due to an abnormal foetal cardiotocograph. Investigations showed severe hypercalcaemia (4.87 mmol/l), suppressed PTH (0.5 pmol/l), and acute kidney injury (peak creatinine 150 μmol/l). Despite severe hypercalcemia, the patient was asymptomatic except for constipation. The patient wasn’t prescribed any regular calcium or vitamin D supplements. A detailed medication history elicited excessive use (frequently >10 tablets/day) of Rennie’s Spearmint tablets for reflux symptoms during pregnancy. Each tablet contains 272 mg of elemental calcium. She was also taking Pregnacare tablets (200 mg of elemental calcium daily). This equated to a cumulative dose of 2.9 grams of elemental calcium per day. Investigations for other causes of non-PTH-dependent hypercalcaemia were negative and cross-sectional imaging excluded occult malignancy. Hypercalcaemia due to Milk-alkali syndrome was diagnosed. Hypercalcaemia and acute kidney injury resolved with aggressive rehydration with isotonic saline (4-6 L/24 hours) without the need for bisphosphonate therapy. The latter was avoided due to the risk of causing rebound hypocalcaemia. The patient was advised not to take any over the counter calcium supplements. She was normocalcaemic and well at outpatient review. This case highlights the importance of taking a detailed drug history which should include all over-the-counter medications, including antacids. Milk alkali syndrome can easily be overlooked, and a high index of suspicion remains the cornerstone of diagnosis in the absence of obvious causes of hypercalcaemia especially in the pregnant patient.