The impact of subclinical hypothyroidism on core reproductive hormones and ovarian endocrine status in patients with polycystic ovary syndrome: a systematic review and meta-analysis.

OBJECTIVE

This systematic review and meta-analysis aimed to evaluate the effects of subclinical hypothyroidism (SCH) on serum levels of reproductive hormones, including follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol, prolactin, and total testosterone, in women with polycystic ovary syndrome (PCOS) and to provide evidence for clinical practice.

METHODS

We searched PubMed, Web of Science, Embase, and Cochrane Library from inception to 25 April 2026 for relevant observational studies. Study quality was assessed using the Newcastle-Ottawa Scale (NOS). Statistical analyses were performed using R software, with the standardized mean difference (SMD) and 95% confidence interval (CI) used as effect measures. Heterogeneity was evaluated using the I² statistic, followed by subgroup analysis, sensitivity analysis, and publication bias tests.

RESULTS

Thirteen studies involving 3,114 participants (579 PCOS patients with SCH and 2,535 euthyroid PCOS controls) were included. Pooled analyses showed no statistically significant differences in serum FSH, LH, estradiol, or total testosterone levels between groups. For prolactin, a significant elevation emerged after post-hoc exclusion of an outlying study contributing to extreme heterogeneity; this finding is exploratory. No significant publication bias was detected for FSH and LH; however, tests were underpowered for the other three outcomes, and Begg's test suggested potential small-study effects for prolactin. Certainty according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework was low for FSH and very low for LH, estradiol, prolactin, and total testosterone.

CONCLUSION

Current evidence shows no significant differences in FSH, LH, estradiol, or total testosterone levels between SCH and euthyroid PCOS controls, while the evidence for prolactin remains uncertain. High heterogeneity and the observational study designs preclude definitive conclusions or causal inference.Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/view/CRD420261382326, identifier CRD420261382326.