The mitochondrial enzyme 25-hydroxyvitamin D(sub)3 1-alpha-hydroxylase plays an important role in the synthesis of active 1,25-dihydroxyvitamin D(sub)3 in both renal and extra-adrenal tissues such as granulamatous tissue. There is an increased expression of 1-alpha-hydroxlase in sarcoidosis. This can result in hypercalcaemia secondary to elevated 1,25-dihydroxyvitamin D(sub)3.
We present a case of a 81 year old retired GP with long-standing hypercalcaemia associated with a previous history of primary Sjogren's syndrome on the basis of raised anti-Ro and anti-La antibodies. Investigations included elevated corrected calcium 3.06millimoles per litre(2.12-2.62), creatinine 272micromoles per litre(60-125), a negative myeloma and tumour screen, normal 25-hydroxyvitamin D(sub)3 32nanomoles per litre(20-110) and parathyroid hormone 1.6picomoles per litre(0.5-5.5), but raised angiotensin converting enzyme 130units per litre(11-80) and a high active 1,25-dihyroxyvitamin D(sub)3 266picomoles per litre(40-150). Hypercalcaemia responded to hydrocortisone suppression testing. Muscle biopsy showed evidence of active sarcoid myopathy. No evidence of sarcoid was identified elsewhere (normal computerised tomography of chest and abdomen). He also had features of primary autoimmune hypothyroidism and primary gonadal failure the aetiology of which remains uncertain. Ultrasonography displayed bilateral small testicles. Testicular biopsy was declined. He responded well to steroid therapy with normalisation of serum calcium and renal fuction.
In conclusion, hypercalcaemia complicating sarcoidosis is due to active 1,25-vitamin D(sub)3 and investigation of hypercalcaemia should always include measurement of active 1,25-vitamin D(sub)3. We also confirm the association of sarcoidosis, Sjogren's syndrome and autoimmune endocrine disease as suggested by the acronym TOASSUC (Thyroiditis, Other Autoimmune diseases, Sjogren's syndrome, Sarcoidosis, Ulcerative Colitis). In this case primary gonadal failure may be autoimmune or due to sarcoidosis.
24 - 26 Mar 2003
British Endocrine Societies