Endocrine Abstracts

Objective: We describe the short-term normalisation of hypercalcaemia in a patient with NET and PTHrP treated with the somatostatin analog (SSA) octreotide and present a review of extant literature.

Case: A 27 yr old man was referred with resistant hypercalcaemia and a 3 yr history of metastatic NET (corrected Ca²⁺=4.69 mmol/L; NR 2.2–2.6 mmol/L). PTHrP was elevated at 9.5 pmol/L (NR<2.6 pmol/L); PTH=6 ng/L (10–65 ng/L). Hypercalcaemia was refractory to saline rehydration, intranasal calcitonin, and intravenous bisphosphonate. PTHrP fell following a 200 μg octreotide test dose (basal: 8.7 pmol/L; 4 h: 6.5 pmol/L). After initiation of sc octreotide (200 μg tds), serum calcium (baseline 5.6 mM) began to fall after 4 d, reaching a nadir of 2.55 mmol/L after 13 d. However, serum calcium subsequently began to rise, reaching 4 mmol/L 4 months after treatment initiation.

Review: A literature search was carried out on Medline and by hand searching reference lists of identified articles, revealing an additional 6 cases of NET with PTHrP associated hypercalcaemia treated with octreotide. Of the seven cases in total, a short-term normalisation of serum [Ca²⁺] was demonstrated in four, and in each, an acute fall in PTHrP was documented. In three of these four responders, treatment was continued. One patient maintained a normal serum calcium whereas two (including this report) developed recurrent hypercalcaemia within six weeks.

Conclusions: Use of octreotide in NET with PTHrP associated hypercalcaemia may be of value although a sustained response is unusual. The mechanism of tachyphylaxis to octreotide occurring in this context is unexplored. The future use of intermittent treatment, or therapy with an SSA with broader receptor subtype specificity should be considered.

Endocrine Abstracts (2005) 10 P42