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Reduced vitamin D receptor expression in parathyroid adenomas: implications for pathogenesis
D Sudhaker Rao1, Z H Han, E R Phillips
1Bone and Mineral Metabolism Research Laboratory, Department of Medicine, Henry Ford Hospital, Detroit, MI, 48202-2689, USA. danrao50@hotmail.com
Clinical Endocrinology
|September 6, 2000
Summary
Parathyroid adenomas show reduced vitamin D receptor (VDR) expression, likely contributing to increased calcium sensing receptor (CaSR) defects. This explains their slow growth and stable clinical course in primary hyperparathyroidism.
Area of Science:
- Endocrinology
- Oncology
- Molecular Biology
Background:
- Parathyroid adenomas exhibit slow growth, potentially linked to altered secretory set-point.
- Severe uraemic parathyroid hyperplasia involves increased set-point and reduced calcium sensing receptor (CaSR) and vitamin D receptor (VDR) expression.
Purpose of the Study:
- To investigate VDR and CaSR expression in parathyroid adenomas.
- To correlate receptor expression with clinical and nutritional factors in primary hyperparathyroidism.
Main Methods:
- Immunocytochemistry was used to assess VDR and CaSR expression in 24 parathyroid adenomas and adjacent nonadenomatous tissue.
- VDR expression quantified by the proportion of positive cells; CaSR expression by staining intensity using image analysis.
- Patient cohort included a wide range of vitamin D status.
Main Results:
- VDR expression was significantly reduced in parathyroid adenomas (2.93%) compared to nonadenomatous tissue (95.7%).
- CaSR expression intensity was lower in adenomas (151 units) than nonadenomatous tissue (218 units, P<0.001).
- VDR loss and CaSR reduction were independent of race, sex, or disease severity, though CaSR reduction was greater in normal vitamin D status.
Conclusions:
- Reduced VDR expression is a common feature in parathyroid adenomas, likely originating in the tumor's founder cell.
- Decreased CaSR expression may be a primary defect or secondary to VDR loss, explaining the increased secretory set-point and stable disease course.