Endocrine Abstracts

Introduction: Breastfed infants are at risk of vitamin D deficiency because breast milk lacks sufficient vitamin D, particularly if the mother also has low vitamin D levels. Prolonged severe vitamin D deficiency leads to abnormal bone mineralization, resulting in rickets. After starting treatment, there is a risk of hungry bone syndrome due to remineralisation of the bones with significant increase in the bone’s uptake of calcium, phosphate, and magnesium.

Case: A 16-month-old boy presented with afebrile generalized tonic clonic seizure lasted 4 minutes. His diet consisted mostly of breastmilk with minimal solid diet. His mother was not on vitamin D supplement during pregnancy and lactation. There was no consanguinity in the family. No family history of rickets. Blood results showed adjusted calcium 1.44 mmol/l, ionic calcium 0.8 mmol/l, phosphorus 2.04 mmol/l, magnesium 0.85 mmol/l, alkaline phosphatase 731 U/l, iPTH 12.4 pmol/l and 25-OH vitamin D level 22 nmol/l. Left wrist x-rays showed widening and cupping of metaphyseal ends of radius and ulna. Nutritional rickets was diagnosed. He was given one dose of IV calcium gluconate then commenced on oral calcium carbonate (40 mg/kg/day elemental calcium) and colecalciferol 6000 units once a day. The child’s mother was provided with vitamin D supplements. After starting treatment for 5 days, the patient’s adjusted calcium level was back to normal. There was a need for dose titration for calcium carbonate up to 124 mg/kg/day or 3.2 mmol/kg/day of elemental calcium. The phosphate, magnesium and alkaline phosphatase levels were reducing in trend but showed an increase in levels on day 10 of treatment. The 25-OH vitamin D level measured on day 17 of treatment was within the normal range at 128 nmol/l.

Conclusion: Hungry bone syndrome is commonly observed after parathyroidectomy in cases of hyperparathyroidism, but it can also occur during the initial phase of rickets treatment due to the high demands of the unmineralized skeleton. Children recovering from rickets may require higher calcium intake than normal children because of "hungry bones." Magnesium and phosphate should also be replenished as necessary. Monitoring calcium, magnesium, and phosphate levels at the beginning of rickets treatment is essential.