A normal-range PTH may be inappropriate when calcium is high
High serum calcium normally suppresses PTH; a value within the laboratory range may therefore be inappropriately nonsuppressed.
Several explanations may be worth exploring
- Primary hyperparathyroidismPTH may remain high or inappropriately normal despite elevated calcium.
- Familial hypocalciuric hypercalcemiaInherited low urinary calcium excretion can resemble mild primary hyperparathyroidism.
- Medication-associated hypercalcemiaLithium or thiazide exposure can influence calcium regulation.
- Vitamin D or calcium excessSome supplements and conditions can increase calcium levels.
- PTH-independent hypercalcemiaMalignancy and other diseases usually suppress PTH but require appropriate evaluation.