Comparison of Serum Vitamin B12 Levels Among Drug-Naïve and Metformin-Treated Patients With Polycystic Ovary Syndrome

Background Metformin is frequently prescribed for polycystic ovary syndrome (PCOS). There is a well-established causal relationship between metformin use in type 2 diabetes and vitamin B12 deficiency; such a relationship is seldom studied in PCOS. We conducted this study to compare vitamin B12 levels among newly diagnosed and metformin-treated patients with PCOS. Methodology This cross‑sectional comparative study was conducted from July 2021 to June 2022, among patients with PCOS attending a specialized endocrinology clinic of a tertiary hospital in Mymensingh, Bangladesh. A total of 50 patients newly diagnosed with PCOS and 52 with PCOS who had received metformin for at least six months were evaluated. The serum vitamin B12 level was measured by utilizing the chemiluminescent microparticle immunoassay principle. Results The new drug-naïve and metformin-treated subjects with PCOS had similar clinical and laboratory parameters except for the metformin group’s lower hemoglobin levels and higher plateletcrit. Metformin receivers had lower serum vitamin B12 levels than the drug-naïve subjects (385.5 pg/mL [interquartile range, or IQR, 298.7-535.2] vs. 272.0 pg/mL [IQR 217.0-395.7]; P < 0.001). The metformin group had higher frequencies of B12 deficiency and borderline deficiency (15.4% vs. 6% and 42.3% vs. 18%, respectively; P = 0.003). Conclusions This study observed lower serum B12 levels in PCOS patients using metformin than in the newly diagnosed ones. Large-scale data are needed to recommend routine periodic screening for B12 levels in metformin-treated PCOS.