Endocrine Abstracts

Case history: Twenty-one year-old female with Di-George syndrome, genetically confirmed at the age of 6 years, was on 1-alfacalcidol for chronic hypoparathyroidism. Her initial presentation was with Seizures in childhood. She has been seizure free with treatment of hypocalcaemia. Her serum calcium levels have been fluctuating with intermittent hypercalcaemia over the years.

Investigations: Initial results on 1.5 mcg of 1-alfacalcidol OD:

Corrected serum calcium 2.33 mmol/l

Serum phosphate 1.05 mmol/l

Renal functions >60 ml/min per m²

24-h urinary calcium 10.91 mmol/24 h

Renal USS – Evidence of nephrocalcinosis

Follow up results on 1-alfacalcidol 0.75 mcg and 0.5 mcg alternate days with Indapamide MR 1.5 mg OD:

Corrected serum calcium 2.26 mmol/l

Serum phosphate 1.42 mmol/l

Renal functions >60 ml/min/m²

24-h urinary calcium 2.91 mmol/24 h

Results and treatment: Her 1-alfacalcidol dose was reduced to keep serum calcium levels towards lower end of normal; however, despite these measures she remained hypercalciuric and the renal ultrasound showed evidence of nephrocalcinosis. After initial reluctance, her mother agreed for 1-alphacalcidol dose reduction with close monitoring. She was commenced on Indapamide and her 1-alphacalcidol dose was reduced further. Now she remains normocalcaemic at 2.26 mmol/l without hypercalciuria. Gradually we have managed to reduce her 1-alfacalcidol dose from 1.5 mcg once daily down to 0.5 mcg and 0.75 mcg on alternate days. We are considering further dose reduction. Patient remains well and seizure free.

Conclusions and points for discussion: In chronic hypoparathyroid patients 24-h urine calcium is not routinely checked in clinical practice. Renal complications (hypercalciuria 38%, intrarenal calcification 31% and reduction in eGFR 41%) are common in this group. Compared to age matched controls CKD stage 3 or higher is 2–17 fold higher in hypoparathyroid patients. This is due to lack of PTH induced renal tubular calcium reabsorption. Guidelines recommend keeping serum calcium towards the lower end of the reference range (while avoiding symptoms of hypocalcaemia) in order to minimise hypercalciuria and associated complications. 24-h urine calcium should be monitored along with rest of the biochemical monitoring. In those with hypercalciuria, renal stone or reduced eGFR; ultrasound kidneys should be arranged. Thiazide diuretic is shown to reduce urinary calcium excretion and it can be used successfully as demonstrated in this case.