Endocrine Abstracts

We present the case history of a 62 year old male, who was recently diagnosed with sarcoidosis which was confirmed on biopsy of a calf nodule. CT scan revealed pulmonary involvement. Our patient had low vitamin D 12 nmol/l (nr 50–100) and initial adjusted calcium was 2.48 mmol/l (2.13–2.63). DEXA bone density scan revealed osteopenia. He was commenced on loading dose of colecalciferol 40,000 units weekly and received 3 doses. He presented 1 month later with polydipsia, polyuria, bone pains and lethargy. Adjusted calcium went up to 3.69 mmol/l and PTH was low at 0.39 pmol/l (1.1–6.0). At this point vitamin D was 94 nmol/l (50–100) and serum creatinine 156 umol/l (59–104) with baseline creatinine being normal at 76 umol/l. Adjusted calcium remained elevated at 3.5 mmol/l, despite treatment with intravenous pamidronate 60 mg. Our patient received oral prednisolone 40 mg/day and is currently on a tapering dose of prednisolone. The adjusted calcium normalised to 2.35 mmol/l in 15 days.

Discussion: Our case history highlights the importance of replacing vitamin D in patients with sarcoidosis with caution. Alveolar macrophages produces 1-alpha hydroxylase which converts 25-hydroxyvitamin D3 to 1, 25-dihydroxyvitamin D3. Vitamin D replacement results in avidly available, 25-hydroxyvitamin D3 to the macrophages in sarcoid granulomata, leading to excess production of 1,25 dihydroxy vitamin D3, which causes intestinal absorption of calcium and bone resorption leading to raised calcium levels. Another point our case history highlights is the role of corticosteroids in the treatment of hypercalcaemia due to sarcoidosis. Corticosteroids reduce gastrointestinal calcium absorption and inhibit osteoclast function, and are particularly effective in sarcoidosis because of their effects on vitamin D metabolism, as they are potent inhibitors of macrophage 1-alpha hydroxylase.