Effect of L-carnitine supplementation on fertility outcomes among patients with polycystic ovary syndrome: a systematic review and dose-response meta-analysis of randomized clinical trials

This systematic review and meta-analysis of randomized controlled trials (RCTs) assessed the effect of L-carnitine (LC) supplementation on the fertility outcomes of patients with polycystic ovary syndrome (PCOS). Online databases (Scopus, Web of Science, Cochrane Library, EMBASE, and PubMed) were searched to identify eligible RCTs published until March 2024. A dose-response meta-analysis was performed using a random-effects model. Meta-regression was also performed to investigate the source of heterogeneity based on the LC dose and duration of treatment. The pooled analysis included eight RCTs with 1,046 participants. The LC-treated group had significantly increased chemical and clinical pregnancy rates, ovulation rate, progesterone levels, number of preovulatory follicles >17 mm in diameter, and endometrial thickness compared to the untreated groups. The meta-analysis model indicated that LC supplementation did not change the serum levels of estrogen and testosterone; however, the dose-response meta-analysis indicated that prolonged LC intake significantly increased estrogen levels. LC supplementation has significant effects on fertility outcomes of women with PCOS. Additional large-scale longer RCTs are required to confirm the findings of this study.