Endgames Case report

A woman with hypophosphataemia and raised alkaline phosphatase

BMJ 2010; 340 doi: https://doi.org/10.1136/bmj.b5564 (Published 21 January 2010) Cite this as: BMJ 2010;340:b5564
  1. Joanne K Y Lam, resident ,
  2. Karen S L Lam, professor,
  3. Kathryn C B Tan, associate professor,
  4. Wing-Sun Chow, associate consultant,
  5. Annette W K Tso, assistant professor ,
  6. Annie W C Kung, professor
  1. 1Queen Mary Hospital, 102 Pok Fu Lam Road, Hong Kong
  1. Correspondence to: A W C Kung awckung{at}hku.hk

    A 73 year old woman was referred because of hypophosphataemia and raised serum alkaline phosphatase. She was a chronic hepatitis B carrier and regular monitoring had shown a persistently raised alkaline phosphatase (415-495 U/l; normal range 47-124). All other liver enzymes were within the normal range, and ultrasound of the liver was unremarkable.

    Further assessment showed low serum phosphate (0.51-0.63 mmol/l; 0.88-1.45), but normal albumin adjusted calcium (2.53-2.63 mmol/l; 2.24-2.63) and creatinine (40 µmol/l; normal 49-82). Her serum parathyroid hormone was extremely high at 689 ng/l (normal 9-52), serum calcidiol (25-hydroxyvitamin D) was low at 23.5 nmol/l (normal >50), and serum calcitriol (1,25-dihydroxycalciferol) was raised at 240.5 pmol/l (60.2-158.6).

    She was diagnosed with vitamin D insufficiency with secondary hyperparathyroidism and was prescribed cholecalciferol 800 IU/day. After three months of treatment, serum phosphate remained persistently low at 0.52 mmol/l and she had developed hypercalcaemia (albumin adjusted calcium 2.73 mmol/l). Her 24 hour urine for calcium was normal (7.1 mmol/day; 2.0-7.4) and parathyroid hormone remained raised at 691 ng/l.

    Questions

    • 1 What is the most likely diagnosis?

    • 2 What further investigations are needed before treatment can be started?

    • 3 What is the treatment of choice?

    Answers

    1 What is the most likely diagnosis?

    Short answer

    The patient has primary hyperparathyroidism; vitamin D replacement seemed to unmask the hypercalcaemia.

    Long answer

    Primary hyperparathyroidism is a common endocrine disorder. Up to 80% of patients have no symptoms of hypercalcaemia and only a small proportion present with associated complications such as hypercalciuria, renal stones, osteoporosis, and fractures.

    Vitamin D insufficiency is also a common problem worldwide, which often goes unrecognised. A serum calcidiol concentration of below 50 nmol/l is suggestive of vitamin D insufficiency. Recently, the National Institute of Health of the United States recommended a calcidiol value of greater than 75 nmol/l to reduce fracture risk, improve lower extremity function, and protect against development of colorectal cancer. …

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