PTH and Hypocalcemia: Patients with PTH-resistant hypocalcemia may have several mutations in transcription factor proteins including glial cells missing protein (GCM2), T box-1 mutations (TBX-1), SRY Box 3 (SOX3), GATA-binding protein 3 (GATA3), and tubulin-specific chaperone E. These mutations confer a resistance to PTH and vitamin D3 by affecting vitamin D3 receptor and PTH receptor expression.