[Problem] To provide a freeze-dried preparation containing a high-purity PTH peptide and a method for producing the same, and to provide a method for detecting PTH analogs in order to confirm the purity of the freeze-dried preparation containing a PTH peptide. [Solution] The presence of PTH analogs generated during a step for producing a freeze-dried preparation containing a PTH peptide in the present invention was confirmed. It was discovered that the generation of PTH analogs can be significantly prevented or reduced by inhibiting exposure to air inside a facility for producing a PTH peptide-containing solution or the like.
