Effect of Phototherapy on Calcium Metabolism and Bone Mineral Density in Full-term Neonates

Background Jaundice is a common cause of morbidity in the first week of life. Phototherapy (PT) has a considerable role in the management of hyperbilirubinemia in newborns. Hypocalcemia is an uncommon but possible complication of phototherapy (PT). Suppression of the pineal gland, suppression of parathormone hormone (PTH) secretion and increased urinary calcium (Ca) excretion are the proposed mechanisms for hypocalcaemia development after phototherapy. Aim To evaluate the effect of PT on Ca metabolism and bone mineral density in fullterm neonates. Methods This study included 40 full term newborns divided in to 2 groups 20 cases and 20 controls aged from 2 to 8 days. DXA scan was done at base line and at one month using lunar prodigy primo (GE healthcare) for both cases and controls. They were examined for the effect of PT on serum levels of calcium, magnesium, phosphorus, vitamin D, parathyroid hormone, and alkaline phosphatase (ALP) at base line and after 48 of phototherapy. Results The incidence of hypocalcemia increased from 15% pre phototherapy to 21.1% post phototherapy though non-significant. No statistical significant difference in median serum magnesium, alkaline phosphatase and vitamin D between pre and post PT. There was significant decrease in mean serum phosphorus in follow up lab in both study groups. There was significant decrease in arms and L1-4 BMD post phototherapy. There was positive correlation between serum calcium delta change and BMD leg delta change in cases. Conclusion Phototherapy for neonatal hyperbilirubinemia exerts a specific, measurable effect on bone density, particularly in the limbs, while not significantly altering the risk of hypocalcemia. Our findings suggested that phototherapy has a targeted influence on bone metabolism independent of major shifts in calcium homeostasis.