Endocrine Abstracts

Introduction: Asymptomatic hypercalcaemia in infants who are exclusively breast-fed is recognised in clinical practice but has never been evaluated and outcomes described if breast feeding is continued.

Objective: We conducted a novel retrospective analysis to evaluate the biochemical and radiological outcomes of breast milk-induced hypercalcaemia.

Methods: A multi-site retrospective study was conducted across a 4 year period in infants noted to be hypercalcaemic (serum corrected Calcium (CCa) ≥2.8 mmol/L) who were exclusively breast-fed and did not have other medical conditions causing hypercalcaemia. Clinical, biochemical and radiological parameters were collected and analysed.

Results: 18 infants (10 males, 8 females) were included in the analysis. Mean peak serum corrected calcium was noted to be 3.1 mmol/L (normal range 2.2-2.8 mmol/L; standard deviation 0.2). All infants were exclusively breastfed during the detection of hypercalcaemia and were clinically asymptomatic. None of them had interventions such as locasol, intravenous fluids, diuretics or bisphosphonates. Mean serum PTH level was 0.9 pmol/L (low; reference 2.0 – 9.4 pmol/L); mean serum Vitamin D was 60.8 nmol/mL (normal; reference >50nmol/L); and mean serum phosphate level was 1.7 mmol/L (normal; reference: 1.3 – 2.6mmol/L). There was no significant correlation of peak serum cCa with corresponding PTH, phosphate and Vitamin D levels and no significant correlation between age of resolution of peak CCa and duration of breast feeding (P<0.05). All 18 infants had renal ultrasound, and all of them had no evidence of nephrocalcinosis on ultrasound. Mean duration of resolution of hypercalcaemia was 123 days with a range of 10 days to 329 days. Mean duration of exclusive breastfeeding was 108 days.

Conclusion: Breast milk-induced hypercalcaemia is characterised by PTH-independent hypercalcaemia. Unlike other causes of PTH-independent neonatal hypercalcaemia, it is an asymptomatic condition with no nephrocalcinosis. In view of its comparative benign clinical course, such infants with asymptomatic hypercalcaemia and absence of nephrocalcinosis can safely continue to breast feed rather than switching to low calcium formulas, which would result in loss of the many benefits of breast milk. The cause for hypercalcaemia in these infants is not yet established and would require further research.