VD supplementation in women with PCOS increased VD levels and led to shorter menstrual cycles, reduced hirsutism (Ferriman–Gallwey score), lower triglycerides, and a decreased TGF-β1-to-sENG ratio, highlighting VD’s potential role in improving lipid metabolism and inflammation in PCOS. The gene discussed is TGFB1; the disease is Hirsutism.