Surprised no one has given you a personal recommendation yet. We can't do that, but we can offer some option for you to explore: US Biological has a mAb vs. Human PTH 1-34, suitable for WB. Our general listings are here: https://www.linscottsdirectory.com/antibodies?q=PTH%201-34
just select WB from the Applications filter and follow "More Info" to suppliers' pages.
I would recommend an antibody database available at www.labome.com. For antibodies to PTH, you can check this link: https://www.labome.com/gene/human/parathyroid-hormone-antibody.html. You can see the description of these antibodies and references following the links to the suppliers. Santa Cruz offers several goat polyclonal antibodies to human PTH for WB. Also, Abcam has mouse monoclonal (1B10) ab for WB. In addition, EMD Millipore offers anti-PTH mouse monoclonal (3D1.1) for WB. Hope this comment is helpful.