Effect of phototherapy on plasma levels of GH, LH and FSH in the newborn.

Plasma levels of GH, LH and FSH were measured in 74 three-day-old newborn infants with hyperbilirubinemia before and after exposure to continuous phototherapy (PhT) for 48 h. The results obtained were compared with data observed over the same period of time in 46 newborn infants belonging to the control group having homogeneous characteristics as far as form of delivery (spontaneous), gestation age, chronological age, sex, birth weight and basal blood glucose were concerned, except hyperbilirubinemia and necessity of PhT. Hyperbilirubinemic female newborn showed higher plasma GH concentrations in comparison with hyperbilirubinemic males and with controls. Forty-eight of continuous PhT significantly reduced GH levels which, however, appeared not to be substantially different from those of normal controls of the same age. Moreover, PhT determined a slight trend to increase in FSH of females, and did not modify the physiological decline of LH in both sexes during the first five days of life. The reduction of GH following PhT from abnormal to physiological concentrations may be due to the direct effect of light and/or to continuous light-related disorders of sleep. In conclusion, 48 h of continuous exposure to light (PhT) do not impair the newborn's pituitary functions here studied.