Hypercalcemia in metastatic GIST caused by systemic elevated calcitriol: a case report and review of the literature.
BACKGROUND
Hypercalcemia is the most common oncologic metabolic emergency but very rarely observed in patients with gastrointestinal stromal tumour, which is a rare mesenchymal malignancy of the gastrointestinal tract. We describe a case of hypercalcemia caused by elevated levels of activated vitamin D in a patient with gastrointestinal tumour. Prior to this case report, only one paper has reported an association between hypercalcemia, gastrointestinal stromal tumours and elevated levels of vitamin D.


METHODS
An otherwise healthy 70-year-old Caucasian woman, previously treated for duodenal gastrointestinal stromal tumour, was diagnosed with liver metastasis, and relapse of gastrointestinal stromal tumour was confirmed by biopsy. At presentation, the patient suffered from severe symptoms of hypercalcemia. The most common causes of hypercalcemia, hyperparathyrodism, parathyroid hormone-related peptide secretion from tumour cells, and metastatic bone disease, were all dismissed as the etiology. Analysis of vitamin D subtypes revealed normal levels of both 25-OH Vitamin D2 and 25-OH Vitamin D3, whereas the level of activated vitamin D, 1,25 OH Vitamin D3, also referred to as calcitriol, was elevated.


CONCLUSIONS
The fact that plasma calcitriol decreased after initiation of oncological treatment and the finding that hypercalcemia did not recur during treatment support the conclusion that elevated calcitriol was a consequence of the gastrointestinal stromal tumour. We suggest that gastrointestinal stromal tumours should be added to the list of causes of humoral hypercalcemia in malignancy, and propose that gastrointestinal stromal tumour tissue may have high activity of the specific enzyme 1α-hydroxylase, which can lead to increased levels of calcitriol and secondarily hypercalcemia.
Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Tage-Hansens Gade 2, DK-8000, Aarhus, C, Denmark. katrhygu@rm.dk.
Katrine
K
Hygum
Department of Oncology, Aarhus University Hospital, Nørrebrogade 44, DK-8000, Aarhus, C, Denmark. chriwulf@rm.dk.
Christian Nielsen
CN
Wulff
Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Tage-Hansens Gade 2, DK-8000, Aarhus, C, Denmark. torbhars@rm.dk.
Torben
T
Harsløf
Department of Oncology, Aarhus University Hospital, Nørrebrogade 44, DK-8000, Aarhus, C, Denmark. andboy@rm.dk.
Anders Kindberg
AK
Boysen
Department of Oncology, Aarhus University Hospital, Nørrebrogade 44, DK-8000, Aarhus, C, Denmark. philross@rm.dk.
Philip Blach
PB
Rossen
Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Tage-Hansens Gade 2, DK-8000, Aarhus, C, Denmark. bente.langdahl@aarhus.rm.dk.
Bente Lomholt
BL
Langdahl
Department of Oncology, Aarhus University Hospital, Nørrebrogade 44, DK-8000, Aarhus, C, Denmark. akmal@aarhus.rm.dk.
Akmal Ahmed
AA
Safwat
D000368:Aged; D014408:Biomarkers, Tumor / Q000097:blood; D002117:Calcitriol / Q000097:blood*; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000097:blood* / Q000150:complications / Q000175:diagnosis*; D046152:Gastrointestinal Stromal Tumors / Q000097:blood* / Q000150:complications / Q000175:diagnosis*; D006801:Humans; D006934:Hypercalcemia / Q000097:blood* / Q000150:complications / Q000175:diagnosis*
D014408:Biomarkers, Tumor; D002117:Calcitriol