Peptide antigens corresponding to amino acid residues 2-12, 1-12, 2-15 and 1-15 of parathyroid hormone (PTH), antibodies having an affinity to such peptide antigens and methods of producing the same. Such antigens, antibodies and methods producing the same according to the present invention are useful in determining bioactive intact PTH levels in serum, plasma, and/or cell culture media. Such antibodies further possess a high degree of species cross-reactivity, but substantially mitigated cross-reactivity to non-whole PTH peptide fragments and little to no recognition of the first amino acid residue of PTH.