In a rat model of SH, activation of the EGF receptor (EGFR) by TGF-alpha is required for the development of parathyroid hyperplasia, but the relationship between EGFR activation and reduced VDR content is unknown.
In secondary hyperparathyroidism (SHPT), enhanced parathyroid levels of transforming growth factor-α (TGFα) increase EGF receptor (EGFR) activation causing parathyroid hyperplasia, high parathyroid hormone (PTH) and also reductions in vitamin D receptor (VDR) that limit vitamin D suppression of SHPT.