PTH (intact)
What it measures, and what changes the number.
Parathyroid hormone is made by the small parathyroid glands in the neck and is the main hormone that controls calcium and phosphate balance, acting on bone, kidneys and, through vitamin D, the gut. The intact PTH test measures the full-length active hormone rather than its fragments.
It is almost always read alongside calcium, because the two regulate each other, and commonly with phosphate, vitamin D (25-OH), magnesium and creatinine to reflect kidney function.
PTH follows a daily rhythm, so many labs prefer a morning sample, sometimes fasting. The hormone is fragile; samples collected in EDTA tubes and separated promptly tend to be more stable. Different assay generations recognise slightly different parts of the molecule, so results from different labs or methods may not match. Reports may show it as Paratohormona intacta (PTH).
Often read alongside: Calcium (total), Phosphate, Vitamin D (25-OH), Magnesium, Creatinine