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Spontaneously occurring antibodies to parathyroid hormone
M Wilkinson1, A McElduff, J Wilson
1Department of Endocrinology, Royal North Shore Hospital, St. Leonards, New South Wales, Australia.
The Journal of Clinical Endocrinology and Metabolism
|June 1, 1990
Summary
Elevated parathyroid hormone (PTH) levels in a patient were caused by autoantibodies, not hyperparathyroidism. This discovery explains misleading diagnostic results and prevents unnecessary medical procedures.
Area of Science:
- Endocrinology
- Immunology
- Clinical Chemistry
Background:
- Diagnostic assays for parathyroid hormone (PTH) are crucial for endocrine evaluation.
- Misinterpretation of immunoassay results can lead to inappropriate clinical decisions and interventions.
Observation:
- A patient with acute pancreatitis presented with borderline high serum calcium and elevated immunoreactive PTH.
- Initial C-terminal PTH assay results suggested hyperparathyroidism, leading to consideration of neck exploration.
- Further analysis revealed a circulating immunoglobulin M (IgM) component that bound to PTH.
Findings:
- The patient's serum contained anti-PTH IgM autoantibodies, which interfered with the radioimmunoassay (RIA).
- These autoantibodies bound both the C-terminal and intact (PTH-(1-84)) forms of PTH, causing falsely elevated measurements.
- The autoantibodies were spontaneously occurring and not associated with any known underlying condition.
Implications:
- This case highlights the potential for autoantibodies to cause pseudohyperparathyroidism, leading to diagnostic challenges.
- Awareness of such phenomena is essential for accurate interpretation of PTH levels in clinical practice.
- Understanding autoantibody interference can prevent unnecessary invasive procedures and guide appropriate patient management.