Hormonal Variation in Premenopausal Female Athletes Is Associated With Risk Factors for Shoulder Instability: A Systematic Review.

Purpose: To investigate the impact of hormonal variation and the menstrual cycle on risk factors for shoulder instability. Methods: A systematic review was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines using the electronic databases MEDLINE (PubMed), Embase, SportDiscus (Ebsco), and the Cochrane Library. Studies were included if they focused on the impact of the menstrual cycle on the shoulder joint, were published from 2000 to 2024, and were peer-reviewed articles. Results were analyzed and synthesized, and a risk-of-bias analysis and quality assessment were subsequently performed. Results: Of the 124 studies identified in the initial search, 4 met the inclusion criteria and were included in this review. In total, 129 female patients were included, and the mean patient age was 23.3 years (range, 18.1-25.4 years). For every 1-pg/mL increase in serum relaxin levels, patients were 2.18 times more likely to present with acute shoulder instability. Proprioception, specifically in detecting changes in external rotation and flexion angles through the shoulder joint positioning test, was significantly lower in the luteal phase than in the ovulatory phase of the menstrual cycle. Finally, strength in abduction, internal rotation, and external rotation was higher in the ovulatory phase of the menstrual cycle than in the follicular or luteal phases. Conclusions: In this study, we found that physiological limitations in strength and proprioception occur during the luteal phase of the menstrual cycle. We also observed a relationship between increasing serum relaxin levels and shoulder instability. Level of Evidence: Level III, systematic review of Level II and III studies.