@colleenyoung - Hi Colleen, I wonder if you can point me in the right direction. I am looking for information regarding "LOW" Parathyroid Hormone-Related Peptide (PTH-rP). I found a lot of information about High PTH-rP; however, did not find anything regarding Low PTH-rP.
Here is the reason for my request:

As you may remember, I have had Melanoma and more recently, Breast Cancer. In July 2019 (right before the discovery of my breast cancer), routine labs found High levels of Calcium. My PCP tested the PTH level, which was normal, so nothing else was done. In March 2020, I was admitted to the hospital with nausea, vomiting, and hypercalcemia. The Nephrologist on staff, now my doctor, has been looking for the cause of the Hypercalcemia since that time.

Labs in mid-April showed High Calcium, but Normal PTH and Phosphorus. Labs in mid-June showed the Calcium had decreased to the “upper limit” of Normal: "10.4" (Quest range: 8.6-10.4 mg/dl). PTH and Phosphorus were Normal. However, the PTH-Related Peptide (measured for the FIRST time), was very low: "8 pg/ml" (Quest range: 14-27 pg/ml).

The Nephrologist is puzzled. Because of the low PTH-rP, 3days ago he decided to order a "Sestamibi scan". However, by the afternoon, he had changed his mind; he now wants to wait another 2 months and get new labs to see if anything changed. I really don't do "waiting" too well; so, in the meantime, I would like to understand more about the low Parathyroid Hormone-Related Peptide.

Thanks Colleen!

-- Dee