Cosecretion of Glycosylated Prolactin and Non-Glycosylated Prolactin from Childhood to the End of Puberty

Abstract

Background: Glycosylated prolactin (G-PRL) is considered as the major post-translational modification of prolactin (PRL) showing reduced lactotropic and mitogenic activities compared to non-glycosylated prolactin (NG-PRL). Aim: To evaluate the evolution of G-PRL in normoprolactinemic children and adolescents and to analyze possible variations in glycosylated/total prolactin (T-PRL) ratios. Methods: T-PRL, G-PRL and NG-PRL were evaluated in 111 healthy female and male children and adolescents (4.1–18 years), classified as group 1 (Tanner I), group 2 (Tanner II–III) and group 3 (Tanner IV–V). G-PRL and NG-PRL were identified by chromatography on concanavalin-A-Sepharose. Results: G-PRL/T-PRL (median-range): females, group 1: 0.59 (0.17–0.77), group 2: 0.56 (0.31–0.78), group 3: 0.60 (0.38–0.79); males, group 1: 0.64 (0.39–0.80), group 2: 0.61 (0.24–0.79), group 3: 0.62 (0.35–0.90); the p value is not significant among the different groups in both genders. G-PRL/T-PRL ratios do not change when comparing low (first quartile) versus high (third quartile) T-PRL levels in the different groups. Conclusion: Our study would appear to support cosecretion of G-PRL and NG-PRL from childhood to the end of puberty. Such cosecretion would not be dependent on sex steroid levels. It is important to point out that puberty does not change the proportions of G-PRL and NG-PRL.