Background: Systemic lupus erythematosus (SLE) is an autoimmune disease with multiorgan involvement and wide variability in presentation and course. Although it can appear at any age, women of childbearing age are primarily affected. This has led to the proposal of a hormonal role in the development of SLE. Among the main hormones shown to have immunomodulatory effects are estradiol, progesterone and prolactin.

Objectives: To report the levels of estradiol and prolactin in SLE patients and establish the relationship between these levels and disease activity, and to determine whether the phases of the menstrual cycle influence the activity of SLE and its relationship to hormone levels.

Methods: In this cross-sectional study, we examined 60 women with SLE. We measured disease activity using SLEDAI and BILAG. We obtained peripheral blood samples to determine the levels of estradiol, progesterone, and prolactin. 

Results: Patients’ age ranged between 16 and 65 years and the mean disease duration was 5.5 years (0–20). SLE was active (SLEDAI > 6) in 13 patients and inactive in 47. Thirty patients were in a pre-ovulatory menstrual cycle phase, 13 in a post-ovulatory cycle, and 17 were menopausal. We found a significant association between C4 levels and disease activity (P = 0.01) and between estradiol levels and disease activity in the kidney (P = 0.04). We did not find hyperprolactinemia in any patient. 

Conclusions: In this population, we found an association between estradiol levels and organ-specific activity in the kidney. One may speculate as to whether our population might benefit from the implementation of anti-estrogen therapy for control of disease activity, particularly in the kidney.