Endocrine Abstracts

We have previously demonstrated that 80% of patients with PTHP will have co-existing vitamin D deficiency suggesting an increased metabolism of vitamin D. There are few data assessing the impact and safety of different vitamin D preparations on calcium, parathyroid hormone (PTH) and vitamin D in this group. Here, we report the details of replacement therapy using different vitamin D preparations. In a retrospective study of 22 (20F:2M and 8 Asian:14 Non-Asian) patients with confirmed PTHP and vitamin D deficiency, we assessed the impact and safety of treatment with osteo-D2 50,000 IU after four-eight weeks (n=8), calcium and vitamin D (e.g. Adcal-D3) twice daily for three months (n=6) and over the counter (OTC) vitamin D 1000IU/day (n=6) or cod liver oil (n=2) for three months, on serum calcium, PTH and vitamin D levels.

Results: See Table. Mean (±SD) serum calcium was statistically significantly increased after treatment in the group as a whole {2.7(±0.23) vs 2.75 (±0.28) mmol/L; P<0.05} and also in those treated with osteo-D2 50,000IU {2.69(±0.22) vs 2.76 (± 0.25) mmol/L; P,0.05}. Patients with a pre-treatment calcium of >3 mmol/L (n=3), did not have a clinically significant increase in their mean serum calcium (3.18 vs 3.22 mmol/L). Eighteen of 22 patients were vitamin D replete in 2–3 months.

Conclusion: These data suggest that vitamin D repletion, regardless of the treatment regimen used, in patients with PTHP and co-existing vitamin D deficiency is safe. Moreover, treatment does not clinically significantly exacerbate hypercalcaemia for the majority of patients. We would still however, advocate close monitoring of calcium levels in these individuals. Finally, despite the increased metabolism of vitamin D in PHPT, most patients will be replete within 2–3 months regardless of vitamin D preparation.

Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.