Serum Calcium and Melatonin Levels in Neonates Undergoing Phototherapy.

Phototherapy-induced hypocalcemia has been postulated to result from a decline in serum melatonin levels. The present observational study evaluated the effects of phototherapy on serum calcium and melatonin levels, and assessed their correlation, if any. Eighty-nine neonates with a total serum bilirubin levels of 14.1 ± 2.8 mg/dL were recruited at the mean age of 51.9 ± 21.7 h. After a median interquartile range (IQR) duration of phototherapy for 24.0 (24-25.5) h, serum calcium levels decreased significantly, from 9.6 ± 0.8 to 9.4 ± 0.6 mg/dL; p = 0.02, leading to asymptomatic hypocalcemia in 2.2% of the neonates. Median (IQR) serum melatonin levels also decreased from 187.8 (133.5-227.6) to 176.3 (145.6-202.5) pg/mL after phototherapy, the difference being statistically insignificant. No significant correlation was documented between the duration of phototherapy with calcium and melatonin levels. The authors conclude that phototherapy resulted in a small but significant reduction of serum calcium levels without any significant correlation with serum melatonin.