In secondary hyperparathyroidism (SHPT), EGFR activation of the protein kinase B (PKB, commonly named as AKT)-mTORc1 pathway triggers phosphorylation of downstream substrates S6 kinase1 (S6K1) and ribosomal protein S6 (rpS6), leading to parathyroid cell expansion. The gene discussed is RPS6; the disease is secondary hyperparathyroidism.