Tu Qinghua et al. studied 46 gynecomastia patients and 38 controls, finding significantly higher serum progesterone levels in gynecomastia patients (70.1 ± 9.2 ng/mL vs. 70.3 ± 8.8 ng/mL) and a markedly higher PR-positive rate in affected breast tissue compared to the unaffected side (78.13% vs. 28.13%, p < 0.05). Here, PGR is linked to Gynecomastia.