Hyperprolactinemic patients are prone to increased protein oxidation: a risk for low grade inflammation?

I Cakir; G Baskol; G Elbuken; Z Karaca; M Mert; Y Simsek; F Bayram

Objective: Hyperprolactinemia is reported to be associated with impaired glucose metabolism, and low-grade inflammation. There is some data regarding increased oxidative stress- particularly protein oxidation in the conditions like metabolic syndrome or diabetes, but not in hyperprolactinemic subjects in the literature. We aimed to investigate advanced oxidation protein product (AOPP) levels-an established marker of protein oxidation and antioxidant thiol levels in hyperprolactinemic patients with prolactinomas.

Patients and Methods: Thirty- four patients (24 women and 10 men) with prolactinoma, aged 37.50±10.98 years and twenty (age, gender and BMI matched) healthy volunteers as a control group were enrolled to the study. The patients with macroadenomas and mass effects were underwent to transsphenoidal adenomectomy, while the others received medical therapy with a dopamine agonistic agent- cabergoline (1–8 mg/week). AOPP and thiol levels were measured at baseline and after 3–6 months following normalisation of prolactin levels.

Results: Advanced oxidation protein product levels were higher in patients compared to healthy controls at baseline (P=0.002), a significant decrease was observed in patient group following prolactin normalisation. Thiol levels were found to be increased in hyperprolactinemic patients and remained higher (P=0.016, P=0.008 respectively) after treatment.

Conclusion: Our results revealed the presence of protein oxidation in hyperprolactinemic patients. We conclude that thiol levels increase to protect these patients from oxidative stres. The controlling duration may not be enough long to observe normalization of antioxidant thiol levels. Further studies are required in order to determine the role of oxidative stress in the pathogenesis of impaired glucose metabolism, and low-grade inflammation seen in hyperprolactinemic patients.

Key Words: Hyperprolactinemia, oxidative stres, AOPP, thiol.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.

**Table 1** Comparison of patients and healthy volunteers before and after treatment.
	Levels of AOPP (μmol/l)	Levels of thiol (μmol/l)
Patients before treatment n=34	400.03±208.15 349.61 (258.97–582.84)	215.21±60.64 225.61 (188.26–250.76)
Patients after treatment n=29	316.32±175.41 277.68 (179.61–394.29)	215.41±46.40 207.32 (185.98–254.57)
Healthy volunteers n=20	275.85±143.52 261.87 (169.77–287.19)	177.56±53.59 179.88 (153.96–216.46)
P Before treatment - after treatment	0.002	0.682
P Before treatment - healthy volunteers	0.003	0.016
P After treatment - healthy volunteers	0.314	0.008

Endocrine Abstracts

P1411