When sourcing hormone powders (such as steroid hormones, peptide hormones, or estrogen derivatives), the purity level is the most critical metric, typically requiring a minimum of 98% to 99% as verified by HPLC (High-Performance Liquid Chromatography). Buyers must request a COA (Certificate of Analysis) for every batch, which should include results for Heavy Metals (Pb, As, Hg < 10ppm), Loss on Drying, and Residual Solvents. Additionally, ensure the product meets international pharmacopoeia standards such as USP (US Pharmacopeia), BP (British Pharmacopeia), or EP (European Pharmacopeia) to guarantee chemical stability and efficacy.