Endocrine Abstracts (2018) 55 CB7 | DOI: 10.1530/endoabs.55.CB7

A case of hypercalcemia with normal 25-OH vitamin D levels, post-treatment with high dose cholecalciferol for low vitamin D levels

Ryizan Nizar & Tony Robinson

Royal United Hospital, Bath, UK.

79 year old male had been admitted due to multiple falls within a space of 24 hours. On admission, he had a full set of bloods which showed hypercalcaemia and no other significant abnormality. His past medical history included Prostate Cancer, Type 2 Diabetes and Urinary retention for which he had a long-term catheter in situ. His current medications were Linagliptin, Apixaban, Bicalutamide and simple analgesia. Initially, he was fluid resuscitated, which seemed to improve his calcium slightly but his calcium levels remained well above 3 despite fluid rehydration so he went on to have intravenous Pamidronate as per trust protocol. Despite this his calcium levels stayed above 3 mmol/l even after 48 hours, so he went on to have a 2nd dose of Pamidronate which also had little effect on his calcium level.

Urine BJP- Negative

Serum protein Electrophoresis- Negative

Serum ALP – 68 IU/l

HB 128 g/l

ACE level – 38U/l (8-52)

Normal SST

TSH 5.1 mIU/l

T 4-15.3 pmol/l

PSA – 3.5 μg/l

PTH (on admission) – 1.4 pmol/l (1.6–6.9)

Total Vitamin D 63 nmol/l

Adjusted Calcium 3.27 mmol/l (on admission) (2.2–2.6)

CT Chest/Abdomen/Pelvis – No evidence of Malignancy

Missing link?: During a recent admission, he had a Vitamin D level checked and found to have very low levels. He was loaded on 50 000 Units of Cholecalciferol and was discharged with instructions to take 50 000 units once a week for 5 weeks. However, he was back in the hospital within 3 weeks of discharge and his Vitamin D box was empty. Looking through this patient’s previous calcium levels it was noted he had never had high calcium levels and in fact, if anything at times it was low prior to admission. However, Vitamin D levels at 63 nmol/l they were certainly not very high. We went on to check a 1,25 OH vitamin D level. This level came back at 199 pmol/l (55-139) which was much higher than the normal range.

Discussion: A normal CT scan, as well as a negative serum protein electrophoresis and negative urine BJP, excluded malignancy as a possible cause of his hypercalcaemia. A suppressed PTH at admission prior to treatment also excluded Hyperparathyroidism as a cause. In conclusion, this was a patient with hypercalcaemia due to Vitamin D toxicity with normal serum 25-OH Vitamin D levels and raised 1-25 OH Vitamin D levels.

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